1st, always aim ahead of the fighters. The more far they are, the more ahead you aim. Of course, you'd want to follow their path, so if a fighter is going from right to left, you aim ahead on his left, go it?

Expl#1: fighter --->    *<aim here

Expl#2: aim here>*    <---- fighter

2nd, if your Having trouble with this Mini-Game, here is some advise:

Before you go into the turret Mini-Game, turn your graphic settings's quality down, the lowest option, particularly resolution.

This drastically increases your framerate, which makes shooting the fighters much, much more easier.

3rd, you can use an EZ Turret Mini-Game Mod, this mod offers 2 modes, easy and real easy, refer your self to the read me file for more details.

Or, if you feel that you don't want to do this Mini-Game at all, you can use this Tourret Mini-Game disabler