1. Never turn your back.
You don't want a zombie popping up behind you while you're moving onwards, always remember to check behind you frequently, and keep that magazine loaded!
2. Pick it up FAST!
Don't stop, look at it and ponder, see it from a distance, do you need it?
>Yes. Run up to it, swiftly walk by it and hit e a few times, walk off. Don't walk ontop of it, look at it, press e a few times then wait.
>No. Don't walk up to it and think. Run away from it, ignore it, you don't need it.
3.Remember your communication. Microphone or chat, typing simple messages can save the game, even use the voice commands for that extra assistance.
4. Jump Around! Don't constantly jump all over the place, this will deplete your stamina. When a zombie comes at you, jump, shoot, shoot jump and repeat, it will deter the zombie effectively, unless that zombie has no problem hitting humans who jump.
5. Watch that Stamina! Don't pick up loads of stuff, run around and think 'why am I getting slower and slower?' keep an eye on that stamina meter. If it's low and you're safe, stop moving, if it's low and you're being attacked, Panic! If it's low, but you're outside in the vicinity of danger, just walk for a while.
6. Remember to PANIC! You may all think 'ive shot the zombie enough times, one more mag couldn't hurt' and then had that zombie kill you because of your misjudgment. Just remember, if it's getting closer, don't stick around to see what happens. PANIC!
7. A melee is a good finisher, but not the best starter. Don't try and melee a zombie from full hp unless you know you're good. Damage him as much as possible then move in for the kill.
7. Stick together, and take the shortest route. Don't run off separately. Unless you're Martin, in which case, you should run around with that guy. Even being in as much as a pair can save your guys' hides. Don't take the long way round, if you know your maps well, use the quickest way to get to that objective! And remember to check every route or orifice you see, zombies could come from above, by the sides, and even below!
1. Don't be afraid of them. Make them afraid of YOU! Don't rush in, then run off when you're low on health. Charge! See if you can inflict as much damage as possible. This should only be applied when dealing with a single person, with a group, run home to momma.
2.Whitey roar and quick talk/typing can give away the human's camping position, or possible location to where they are headed. Organise that ambush!
3. Movement is your best friend. Just like with humans jumping, do the same. There's nothing that disorients their aim like a hopping zombie, jump in the air, hit the ground, crouch, jump again, twitch all over the place! It'll put them off shooting you out of fear of wasting ammo, and if they do waste ammo, all the better! They won't hit you(most of the time) And unless the server disallows it, run at them, use one little bit of lunge and jump at 'em!
4. Conserve your lunge. If you don't need to, don't use it. You could build that lunge into a berserk. Only use it if you're about to be detected, rush 'em!
5. Once again, take the quick way. You're giving the survivors an advantage if you're not there to even distract them from their objective, learn your maps and use them short routes!
All I got! (This is what I attempt to use as my guide, as well as what Ripper said.)