I'm trying to get better at it, and as Mutiny can tell you, I'm improving. Very slowly, and very slightly, but improving a little bit. Here are a couple of tips I've learned:
First, keep moving. Find a spot, shoot one or two guys from it, and then MOVE. Unless you're playing team hardcore, those guys you killed have killcams to watch, and they'll hunt you down faster than you'd believe.
Secondly, look for bodies on the ground. These equal normal weapons, which come in handy. Pick up that M16 or MP5 to carry around so you can clear out spots to snipe from, or get that guy that's trying to sneak up on you.
Third, lead your target. The bullet lag means that for sprinting targets you need to aim about a full body width ahead of your victim. Regular running targets about a half of a body width. Walking/stationary targets, of course, just put the crosshairs on their head.
