ahhh best way to learn is to go team style and copy the best guys on your team. like cod mw2 just go team deathmatch and follow a high ranked guyand see how he goes about things. Generel rule is to figure what u like for example i hate camping its boring and i feel like a douche so i try to move constantly and quickly and rely on my reactions oh and check behind you
I usually go in the front and take heavy fire. I like maneuvering around, ducking and hiding behind walls while in a firefight. I also camp sometimes. Though sometimes.
Get tons of ammo and go straight into the center. If I feel that I don't have enough ammo I camp with a long range weapon. I usually try to be stealthy.
going straight to the center on most shooters will earn you a bullet to the head. Just move with your team, establish a base (camp lol) and help every sector. This usually works (as camping always does) until the other team gets nade happy or have a helluva player that can outsnipe your snipers