This tread is very useful if you want to improve your shoting:
http://forum.1cpublishing.eu/showthread.php?t=17279
I'm a bit a "Erich Hartmann person". He's the top ace of all times. He got always very close to his enemy and shot him, it's a good technique. Deflection shooting is useful too, but if you're not good at it, it's a waste of ammo. You have to practice it.
You'll find lots of info at that tread.