[absolute]

I actually turned my mouse sens. up just a little bit.

1. play more..preferably against people better than you. That way you're forced to work harder for your kills.
2. if you find a player that's really good..spectate him for a while..watch what he does..how he tracks people down, handles fights and maneuvers around the map etc. etc.
3. practise straffing and practise it alot. It'll save your ass.
4. play alot...and alot and alot..

that's about all the advice i can give.