Bruv is so right.
Practice, practice, practice.
After a while you will find that you can judge pretty close the distance away of your taget.
I'm by no means a GV'er either, and its taken me alot of offline practice, but if needed i can shut down a small airfeild with a t34, or really make life difficult at med and large feilds. As for gv vs gv ... I really dont have the patience to sit and camp, and I still am a lousy shot on the run.( need to practice more myself:D)
also, HE for buildings, hangers, ect
AP for other GV's
Oh , and I'll pass on the best advice I've received
Have FUN!!!