Don't corner camp, but if you do, make sure the frontal person isn't you, and is crouching/prone. Makes it so everyone can shoot.

Aim for the head, and don't use those rediculous guns with a load of recoil. I like the commando, Thomson on the classic maps or the RPK the best personally.

Try not to get in the way of anyone.

Always watch your back if you're running around/camping and your back isn't covered.

Sometimes you can't revive someone. It's better to run than revive in some situations. Keep in mind who's down though, if it's your best player, the "medic" who's revived everyone 5+ times and only downed that once, then you should probably pick him up.

Nog is your friend, Drink drink drink. Other perks are good too. All in all, I'd get Nog and Speed, and the other two are up to you. Nog for your health, and speed to the speedy reloads, when you're stuck in a corner, and there's a horde coming.

There's more but I'm tired right now, can't really think.