It depends on the map/gamemode. I play Rush a lot and different classes/weapons are better for different bases, or if you are defending or attacking (it's the beauty of this game). But that comes with experience, I've got in close to 500 hours. I would suggest just playing the class you feel comfortable with for now, with obvious exceptions. For example, I wouldn't take engineer on Metro, apart from maybe the third base attacking and only as a last resort if we can't break through. Just a small tip, Assault is the class that is the easiest to play because of the med kit. Take an AEK and medkit and rain down death, but keep throwing the medkit, especially on corners.
Also, about choppers. The best way to practice is to go into server options and select a map with a chopper, like Kharg Island or Kaiser railroad, and find an empty server (very easy, just scroll to the last page). Then just practice your flying. Even after 500 hours I've been doing this for the Scout chopper as I've been useless in it and want to improve.
There are also some good youtube channels offering some good advice. Two of the best are http://www.youtube.com/user/rivaLxfactor and http://www.youtube.com/user/LevelCapGaming Both are on PC but their tips/tutorials are mostly still relevant to console.
Edited by Bananazniper at 11:11:36 19-03-2013
Edited by Bananazniper at 11:20:52 19-03-2013
#9450374, By Battlefield 3 - Gaming/online chats times (pew pew)