Hey TTG
This is a strategy on how to get to round 30+ :
Firstly you need to stay in the first room for first 4 or 5 rounds knifing and shooting to get your points up. Its better to have 3 or 4 people to play with so you don't have to open all the doors.

Now you should have about 3000 - 4000 points, You need to open all doors to the power, use the random box 1-2 times depending on what you get. Then you go to phd flooper and camp there for the 7 - 8 Rounds (you should be on round 5 or 6) Stay there till round 12 to 14.

Now try to leave a crawler and go and buy jugganout. Now you need survive the monkeys round, if you have a ray gun its one hit kill so the round will end pretty quick Now if you have done the monkey round right you will get a free perk at the end of the round. (be careful if it is quick revive or something because you will have to protect that perk as well to get another free perk)Now if there is 3 or 4 of you go would back to phd and buy phd flooper and keep dive bombing down that stairs where the zombies come up to save ammo. do this for a couple of round then leave a crawler at the end and use all the landers to open up the pack - a - punch then pack - a -punch your guns this will help you survive.

know all you have to do now is to go back to phd and stay there for as long as possible, if you fell pressured use the lander then quickly make your way back to a lander area and carry on from there doing the same thing all over again. Hope this helped

Thanks GBAx Fuisionzz 8)