Moving Around

Take advantage of background noise when being stealthy

Running at normal speed makes noise; so does opening moving boxes, and opening grates or vents. Walking instead of running will eliminate the noise you make when moving, but to move or open things you generally must make some amount of noise, potentially giving your position away to the enemy. When you're being stealthy, it's in your best interest to wait until there is ambient noise -- such as gunfire -- to make your move. This way the noise you make is less likely to be noticed among the din. If there's no background noise available, you can make your own -- throw a grenade as a decoy. Take advantage of background firing and grenade explosions to make your move.

Avoid jumping in low gravity (low gravity)

On servers with low gravity, the worst thing you can do is jump. It sends you sailing through the air in a nice, slow arc, making you an easy target. More importantly, though, your firing accuracy is severely reduced when jumping -- most rifles are nearly useless at even short range when in the air. If gravity is low, whatever you do -- don't jump.