Learn the map.
Work as a team.
Be aware of surroundings, exits etc.
wigglewalk, wallrun, strafe run.
aim for the head.
Look for ways to kill zombies without using much ammo (explosive crates on quad17, crusher thing)
Listen for ammo spawns.
Listen for zombie spawns.
Listen for zombie noises.
Check your back a lot.
Observe, so many players seem so tunnel visioned, try not to lock onto one target.
Shoot to kill,
-Always move in groups
-When not camping, always be mobile
-If you pick up ammo for a gun you don't have and the gun is already taken, give the ammo to that user with the gun.
Organize and tell your team which zombie to shoot first.
Take more than one heavy weapon. (depends on number on team) There are 3 ''Heavy'' weapons as far as im concerned, the magnum, the shotgun, and the ar15/m16, one is enough!!.
Make presumptions e.g. yeah he'll kill that zombie.
Snipe with anything but the magnum.
nuke yourself with the c4.
Use your crowbar, you WILL die.
Try to make an ammo run WITH a heavy weapon in your inventory (give it to a friend)
Let an injured zombie get away.
If you dont want your starting pistol dont shoot all the ammo off then throw it away, give it to someone.
Any more tell me and i'll add them