For N00bs, start out with MP5. Its a pretty easy gun to use, and you dont have to worry about pulsing as much as the AK/Colt. Also, if you use the Colt, it is supposedly more accurate (I have found this to be true) with the silencer on, but less powerful.
Also, try to get good with the Desert Eagle. The DE is a really good gun once it is mastered and having it has a secondary weapin, you will own.
And dont forget to JUMP !!!!