Solo is the hardest to get far on in Dead Ops. If you're looking to play a good, long game then play with 2 or 3 people. I recommend 3 as it will be easier in the later rounds to stay alive IMO, but some people say two is better. 4 Players is too many; many more engineers drop and there is less space to work in. 4 player is not recommended.
The number of players does not affect time, as the rounds are set to a certain time limit, not to a certain number of kills. Also, a game to round 40 on DOA only takes about an hour and a half, making it much quicker than regular zombies. Round 99 takes about 13 hours, which is waaaaaaaay shorter than normal zombies. However, Dead Ops is way more action packed then regular zombs. It requires quick thinking and good reaction time throughout every round. There is no set loop that will work for a hundred rounds. Every game of dead ops is completely different from the last, and thats the beauty of it. Even more exciting is that it's a one hit death, making it crucial to stay away from zombies. There are many more little intricacies in Dead Ops than in regular. You always have to pay attention. If you zone out slightly, you WILL die, unlike in regular zombies where you will get hit once and have time to react. Anyways, to the strategy part.

As you should know, you start off the game with 3 lives. You can gain lives up to a maximum of 9. There are a couple ways to get extra lives. The first way is to gain 200,000 points. This is all dependent on your multiplier; it will take 2,000 kills to get an extra life at times 1 multiplier. However, if you are at times 9 multiplier than it will only take 222 kills to get an extra life. Obviously, there is a big difference here. This is the reason you want a high multiplier to increase your score. High Multiplier=More Lives.

The main other way to get a free life is to pick one up off the ground. It will look like a man that is glowing yellow on the edges. Once picked up, all the players on the team will get an extra life, not just the person who picks it up. If someone is reviving while a life is on the ground wait until the life is flashing to pick it up so that your teammate is alive and he will get an extra life instead of being revived by it.

There are also a couple of advanced techniques for getting lives. First, a player on your team should have 9 lives before you attempt these methods. If someone has 9 lives, when they reach the next 200,000 marker they can give their life to a teammate. The first way of doing this is the more simple one. Just walk up next to someone (make sure that you are touching them) and face them. When your next life drops down from the sky, with any luck your teammate will get it and not you.

The other way is to drop lives onto the ground. To do this, you must know presicely when your next life will drop. Keep an eye on your score to do this. When the life is falling towards your head, speed boost towards a corner. With some practice and luck (This method IS tricky) your life will be dropped on the ground. That does not mean, however, that this life is for everyone. Only the person who walks over this life will get it. If everyone already has 9 lives, then don't have anyone pick the life up. The reason for this is that dropped lives will stay there forever (unless picked up). That means if you finish the round and go through any of the doors, the life will still be there. The tricky thing is that maps flip vertically and horizontally, meaning the life will be on the opposite side of the map and the opposite corner. Watch out for this and make sure you don't pick it up. Even better, when you leave this map through a teleporter, the life stays there. So if you are good or lucky enough to beat the monkey and get back to this map, then the life will STILL be there. Pretty Awesome.

Now for the dreaded stealing of lives. If a person with 0 lives dies, he will take a life from someone who has a life. In return for giving a life, the giver receives either 3 nukes, 4 boosts, a tank, or a chopper. This really isn't as bad as it seems. 3 nukes can save your life 3 times, making it the equivalent of 3 lives, unless you have 9 nukes. Choppers and tanks aren't all that good. Generally hope you don't get one of these. After the guy takes a life, if he dies within the next minute then he will not take another life and will be reviving for 1 minute. However, if the person who takes the life stays alive for a couple of minutes and then dies, he will take another life. So "plan" your dieing strategically. Don't take too many lives so that your partner goes down to 0 lives.

Best room in the game. You will enter the room of fate either after round 13, 14, or 15. Arrows will appear at the doors, and you will walk to one of the doors and the game will give you a fate, which is basically a permanent power up. There are four fates- Fortune and Fortitude, Firepower, Friendship, and Furious feet. Fortune and fortitude is IMO the worst of all fates as well as the most complicated, but will still be very helpful.

Fortune and Fortitude a giant gem drops on your head and increases your score multiplier by 1. Every power up, like guns or trash cans, will last twice as long as it did before. This is very helpful when picking up either a helicopter or a tank. They go from lasting 20 seconds to lasting 40 seconds, which seems to last forever. Also, after you die and lose all of your gems, your score multiplyir will be 2X instead of 1X, which is very helpful when you are trying to build lives.

Firepower-This is most people's favorite fate. This fate will give you a death machine that never runs out of ammo. It's a pretty simple fate.

Friendship-will give you an all time bird, so whenever you pick up a gun there is double the firepower. Additionally, every bird you pick up off the ground lasts twice as long as usual, kind of the same affect as fortune.

Furious Feet-This is IMO the best fate of them all. It will make you permanently run super fast, which after TONS of practice, will make dodging zombies fairly easy. Many zombies can't hit you because by the time they swing you are already gone. Also, you automatically start each round with 3 speed boosts, even if you finished the round before that with no boosts left. But if you have more than 3 boosts at the end of a round, you will continue to the next round with that number of boosts.

How to Pick the Fate You Want

This gets to be really easy once you know what you're doing. If you pay attention when a round ends or you go into the room of fate, you will notice that some arrows appear before others do. The order that these arrows appear in the room of fate determines which door has which fate. Once you arrive in the room of fate, DO NOT MOVE!! Moving at all can ruin the arrows by making one not show up, disrupting the order so you don't know which door is which. Be very still and concentrate. Stop the conversation with your buddy. If you're not paying attention, no one will get the fates they want and you will likely have to restart. Memorize the order of the arrows as they come up. The first arrow that appears is fortune and foritude. The second is firepower. The Third is friendship. The Last is furious feet. Now, this method will only work if you are playing in 480p. So if you are playing in 1080p, either guess or ask your teammate if he is playing in 480p so that he can tell you.

Which Fates to Get

I highly recommend having someone get furious feet. It may not seem good at first, but with a lot of practice it is the best fate to have. Always have someone with firepower unless you're joking around. If there is a third player then friendship is way better to have than fortune and fortitude. The extra gun will be of great use in the greater rounds when zombies are very hard to kill and helicopters/tanks do not appear that often. For solo I would either get firepower or furious feet, depending on what you are better with or want to practice with.

Helicopters

Let the green guy get all the helicopters.(if not green guy, then blue, if no blue guy, then red) The reason for this is that when green is in a helicopter all the zombies (except dogs ) will go straight towards the chopper. The only ways to die if green is in a chopper is hitting a pole, getting killed by a dog, or if you get really unlucky an engineer will fall right on you and kill you. So basically if green has a chopper it is an entire map monkey. This gives you a quick break from the action barring dogs. This obviously is not an issue in solo.

Tanks

Tanks are not as good as helicopters because zombies do not die on impact with the tank. they have to be run over with it. The missile launcher also sucks and doesn't kill many zombies. Still though, it is 20 seconds of invincibility. For picking up tanks, if someone is fortune let him get it. If there is no fortune then let whoever is not green get all of the tanks provided they aren't death machine. Death machine should never pick up tanks, choppers, or guns since he as the bigass minigun the whole game.

Dogs

If you see a dog on the map shoot at it immediately even if it is not going for you. Dogs can be a real kller for teams. Make sure you get these guys dead ASAP. You can take 3 dog bites in multiplayer before you die. In solo you can be bit 4 times before you die, making it slightly easier. These bites do not reset over time, so if you get bit once on one round, you will only be able to take 2 more dog bites before you die no matter how many rounds later it is. The exception to this is that when you die, no matter what manner of death, your dog bites reset.

Nukes vs. Boosts

Try to use your boosts before you start using nukes as nukes are way more valuable. This is especially key before round 40 because nukes can really save you on that round. This especially applies to anyone with furious feet because you get 3 per round. Definitely don't panic and use a nuke and a boost simultaneously.

Water Barrels

Water Barrels or trash cans are pretty much the best pick up you can get that's not a gun. Usually you would want the furious feet person to pick this up, as he comes into contact with more zombies and is very helpful to him or her. If there isn't furious feet, then have the host pick these up, all the pick-ups are more effective for the host.

Furious Feet

Makes you run as fast as the furious feet fortune for like 10 seconds. This short burst of speed can save the user's life, so if your fate is furious feet then don't be a **** and pick up these feet. It's not like you run extra extra fast, which would be nice.

Wunderwaffe Balls

These can be extremely helpful in the later rounds. It is a one-hit kill on any level and normally strings about 10 kills together from one ball. Same as the trash cans, you want the furious feet to get these, although it is not as important for him or her to have these than the trash cans.

Teddy Bears

I'm pretty sure that 3arc was high when they made these. Uhh lets make this blue forcefield that makes butterflies when zombies touch it. Then the zombies either turn around or stand still waiting there to hit you Teddy bears are good on the early rounds, but later they don't work well at all. Eventually the zombies just stand still and repeatedly swipe that same spot so they can catch you off guard and kill you. It has also happened many times where zombies seem to hit me from the edge of the teddy bear which doesn't make any sense. They are very glitchy and I recommend running around them and letting them disappearing so you don't get killed because of it. Many times people have been killed for the sole reason that they picked up a teddy bear.

Chickens

When a chicken (bird) appears, Let anyone but the foot guy get it. Furious feet doesn't keep it as long as fortune or friendship and when firepower gets it he has two death machines. These can be really helpful in the later rounds due to doubled firepower.

Autoturrets

Whoever picks these up gets the points and the kills that come from these. They are semi-helpful but can be annoying at times. Autoturrets Aren't affected by fates so anyone can go for these. These aren't worth dieing to get either, so don't stress out if you can't get to it.

Monkey Bombs

These are very helpful, they work exactly the same as they do on regular zombies. They attract zombies but not dogs. If a person picks up a monkey, do not shoot at the zombies on the monkey. Contrary to popular belief, monkeys do not give you double points for kills.

First of all, the person with the fire power fate should not pick up any guns.

Death Machine

Gives you a death machine for a short period of time, same as the fate of firepower. Can be very helpful on the later rounds to push back a line of zombies closer to the door.

Ray Gun

Not as good in Dead Ops as it is in Regular zombies. When you get a ray gun do not shoot at zombies directly, but more at an angle from the side. The ray gun shots will ricochet a couple times, so when you shoot at zombies from an angle, it will be more likely to hit other zombies. Ray Guns are best for taking out a horde of zombie, not the straight lines that come out of doors.

Shotgun

My personal favorite gun in the game. I wish they had an all-time shotgun fate. This is a fully automatic Spas-12 that can mow down zombies. This is very helpful, whoever can get it should take it (except death machine)

China Lake

This is the worst gun you can pick up, although still beneficial in my opinion. It is fully automatic but is not very powerful. China Lakes are good for taking out large groups of zombies. It also creates a lot of smoke so be careful where you are shooting. Make sure you do not endanger yourself or a teammate.

Flamethrower

This is the most risky gun to pick up. Used correctly they can be extremely helpful, but used incorrectly they are a killer. To correctly use a flamethrower shoot away from your teammates, if you shoot at them they won't be able to see themselves or the zombies. Never spin in circles unless your'e on the beginning rounds. When zombies are inflamed, they slow down and their health is significantly weakened, making it easy for the death machine to pick them off.

RPGs

These are extremely powerful and will kill zombies fairly easily no matter the level. The key is to shoot right through zombies so it actually hits them and will continue onto other zombies. Make sure you do not shoot a teammate with RPGs. It will shoot them across the entire map, into a pack of zombies, or into a pole. These are very dangerous to your teammates so just be careful.

Electric Poles

Despite popular belief, electric poles are actually very beneficial to the Dead Ops Arcade player. The poles are off when they are green and on when they are light blue and shocky looking. If you run into a pole that is off, nothing will happen. But if you run into a pole that is on, you will die. The same applies for zombies. Try to use poles strategically and make zombies run into them and die. They can really help you out. But beware, when they turn off zombies will run right through them. So keep your guard up so they do not kill you for lack of paying attention. If you get far enough (usually not until at least the 50s) and are not host, your poles will all turn a grey color, and you will not be able to turn on or off. If this happens to you, make sure you survey the pole positions at the beginning of each round to find the poles as they are difficult to spot when focusing on zombies. Never run through a greyed out pole because it will most likely be on and you will probably die.

Rounds 1-8

These rounds are gimmes, so don't die on them. All you need to do is stay away from the doors so you do not die by accident. Don't just rush for money or a power up, but make sure it is safe to pick it up before you do. (This goes for all rounds but especially the early ones)
There really is no strategy here.

Rounds 9-12

Do NOT go up onto the catwalk, only death happens up there. Stay on the lower level; you may have to run around on these maps, especially if you are solo, so keep your guard up. Still pretty basic stuff on this level, remember to stay away from doors.

Rounds 13-16 (CREEPY CRAWLERS -___- I WILL GET LIKE 2 DOWNS ON THAT STUPID MAP)

These rounds can be tough; even the best die here occasionally. Don't worry if you die once or twice. You will have to move around and start manipulating the zombies on this level because crawlers are strong. If you do get cornered, don't forget to nuke or boost. These are well worth it if it saves your life. On the night map make sure you pay attention to yourself because it gets very hard to see.

Rounds 17-20

These rounds are definitely a step down from the crawler arena as you have your newly acquired fates. Make sure to not stand in the middle and get hit by a cow, those deaths are completely uncalled for and preventable. If an rpg, china lake, tank, or chopper appears do not get it right away!!! Save these until they are flashing fast so you have a better chance to get a golden cow. A golden cow is just a cow that is outlined in glowing yellow. If these cows are blown up, a bunch of gems will spill out of them, which will increase your multiplier. Try not to shoot with these explosives as they will last longer, which creates a higher chance for a golden cow to come out.

Round 21, 23, 24

As long as someone has firepower you can pretty much camp at the top of the steps and have the death machine take most of the kills. It might get a little hectic if they're coming from 3 doors but then either drop a nuke or have someone use a boost to clear things up. These rounds aren't that hard to get by on multiplayer. This is the hardest map solo. I would suggest staying on the lower level and running up the steps as use for a last resort or a good power up only.

Round 22-Downpour

The downpour round can be a little tricky but you want to camp in the corner that is lit green on the upper level. Have death machine do most of the killing... This round depends on death machine holding his own. The only reason for not camping on the stairs is that the engineers (falling guys) might land on you and kill you before you have a chance to shoot him. Camp this map for solo as well, but be wary of the side that you're not shooting.

Rounds 25-28

The only advice I can give for this map is to NOT camp and just move around and manipulate the zombies.

Rounds 29, 31, 32

On These rounds it is possible to camp at the steps where the barriers are. Same as the downpour maps, drop a nuke or use a speed to clear things out if it gets to crazy. These maps are again very easy if camped properly. If you are solo with firepower you will be able to camp but if not then you will have to run around like you would on the other maps

Round 30-Abominable martys

No camping this round, for death will surely take you-two hit markers on your screen by these guys and you are dead. Stay as far away as you can from them-I usually have to use about five boosts to get me through the round alive... don't be afraid to not die.

Round 33, 35-40

There are a couple strategies for these rounds. If someone on your team has furious feet and is decent with it, firepower and whoever else is playing can sort of sit in a corner and let the feet guy run around the whole map. What I mean by this is for firepower to stand a little bit away from the corner and shoot at the zombies from the door closest to him. Here's the tricky part- When zombies are coming from both doors that are right next to you, you have to learn to run straight towards the center of the map and split the zombies. Then move to a different corner and repeat the process. That may take a little time to pick up, but when you do it will be pretty easy to not die. If no one has furious feet you will just have to run around the map and survive. From these rounds out, there is no real strategy for solo, you will just have to run around the map. The best advice I can give is to stay out of corners so as to prevent you from needing to use a boost.

Round 34- The dogs

This is one of the hardest levels in the earlier game, IMO even harder then the boss round. The best thing to do on this map is run yourself into the corner with the most electric poles. Three dog bites(shown by the red tick marks that appear) and you die, unless you got hit by one abominable and haven't died since that round. Then it's just one hit. Really just do your best to kill the dogs. It is likely you will die at least once but you shouldn't die more than three times. However, there is a way to eleminate the threat of dogs, which is by getting the dog bite glitch. Before you start freaking out about people glitching, it isn't really a glitch but a perk- it's just called the dog bite glitch. This is very hard to get even for experienced players like myself. What you have to do to get this perk is not die throughout the whole first 34 rounds. If you do this then you can take unlimited dog bites over a period of time without dieing. But be careful! If 3 dogs bite you at once you will die.This perk carries over into every round until you die. Once you die you will lose the dog bite glitch and you will start dieing from dogs after 3 hits. So the dog bite "glitch" is extremely helpful but very hard to keep and maintain over rounds

Boss Round-The Cosmic Silverback

The key on this round is to have all your nukes and boosts saved up. This is the time to use them, or you will die frequently. Use a nuke when there are zombies in your way and use the boosts when you need to get away from the silverback. The hard part is when the Silverback uses a boost. The two ways to avoid death here are to anticipate the boost and move sideways to avoid it or use a speed boost of your own to get away. You can tell the monkey is about to boost when he roars or pounds his chest. If someone gets a chopper or tank take the monkey to the poles and have him sit on you while the firepower guy nails him. Guns-don't have firepower pick up guns unless he is last alive then he can pick up rpg's. The best gun for the monkey is rpg's. If you are either fortune or bird and rpg's appear, kill yourself (assuming you have an extra life) and sit right up on the monkey with your invinciblity ring and rpg's. Done correctly, this will kill the monkey by itself. Other than that pick up all guns except a flamethrower as that will hurt you in this situation.

Rounds 41-44

Assuming there if a furious feet guy, have death machine and whoever else camp in the corner with the canoe in it. This strategy works extremely well. If zombies are coming from both doors with the canoes, have the foot guy stand by one of the doors and take the zombies from that door. This map is pretty easy if you were good enough to beat 40.

Rounds 45-48

Same as rounds 33 and 35-40

Rounds 49-52

Basically the easiest post 40 map if there is a furious feet guy. For these rounds have the death machine and whoever else camp on the catwalk in a corner where zombies come out of. Death machine can still hold back the door, just don't forget to wiggle and watch for dogs coming from ground level. Also, I highly recommend having at least a X3 multiplyer before going up there so you can rebuild lives. . The foot guy will run on ground level and will get all the money and preferably the choppers and tanks. Piece of cake rounds if done correctly

Rounds 53-56

These are the hardest set of rounds until 80. Small and compact, it is very hard to run around on, but use the same strategy as 45-48. UNLESS you have three people, firepower and friendship fates, and there are at least 4 poles in a corner. What you do if this happens and you are not too confident in yourselves, you can do what is called formation. It is fairly simple and you will only lose one or two lives per round. What you do is have the guy with a single gun, either foot or fortune, and have him jam himself in a corner. The firepower and friendship will both run themselves up to fortune and push against him with your left joystick. If the poles are good they will take out the zombies coming from the two far doors so you only have to worry about the close ones. Firepower shoots at the door closest to him and friendship and fortune shoot at the other close door. If you get lucky on all four maps with poles, these levels will be a cinch.

Rounds 57-60

FYI Round 57 has no cows. These maps can have random poles so do your best to work around them. When I play this is usually a running map for everyone but you can try the strategy from 45-48.

Round 61-64

These rounds are middle of the road difficulty, depending on how good the foot guy is. I've never been here without someone having furious feet so I have no advice for that. Have everyone but foot guy camp up on the steps where you did the first time through, probably will have to use some nukes/boosts. The foot guy will run around on ground level and will have to do his best to stay down there. He can run up through where the guys are camping but shouldn't stay there for more than 15 seconds. If you complete this map on solo, you're freaking amazing at Dead Ops. It gets very tight here and there isn't much room to maneuvre, so if you get past this then you know you've got it going.

Rounds 65-68

Same exact strategy as the first time through

Rounds 69-72

Have everyone but foot camp where they did before and have foot run around. You will have to use a nuke if they are coming from both directions. Can be tricky to get through

Rounds 73-80

Run around not much advice I can give here... you just have to beast it out

Boss Round-Two Cosmic Silverbacks

Same strategy as round 40, but keep in mind the Silverbacks boost much more often. You will need lots of boosts and nukes as well as four or five lives going into the battle to guaruntee a victory on this one.

Rounds 81+

By now you know what you're doing.

Rounds 93-96

Good freakin luck. Get past 96 and you have a new solo world record!

Round 120

The Current CO-OP World Record! Good luck beating that.

So in the long run you have to be patient and have good hand eye coordination. Have a good partner and have a lot of fun and add me to play EZG Dempsey. Sub to my youtube! Youtube.com/user/ExpertZombieGaming