1st off, when you practice at home try snapshooting in the mirror, it's the best way to go. When your actually doing it in a game don't picture yoursef doing this or that or worrying about shooting before you come out. Don't think, just play. you only distract yourself. Out-gunfight the other guy. Basically, before the game starts, trust in your instincts and switch on auto-pilot and just go.