Well, head on, youve gotta hold it REALLY steady, you can practice in the practice modes if u want. Try to fire as near to the enemy as possible, even if u cant quite hit them. Short, slow strokes are good until you can hold it COMPLETELY steady. Shooting close can make unexperienced, less confident players dice out of the way, letting you blast 'em point blank!
Or, considering you don't do quite as well head on, you could hit them in their dive. Even a top-notch head on sniper might take a small duck to get out of the line of fire and throw you off, which is a really bad idea. In a head on, do NOT back down. It gets you shot down by aces, and gives rookies a chance to hit you up close. Still use high sensitivity, of course. *Almost* all of the aces use full. I can get more tips for you if you want.