Two things (at least for me):
Limit diet soda, and keep your blood sugar relatively stable. The chemicals in diet soda I find cause skin problems if I drink any more than 1 every few days. As for the blood sugar thing, I've found that if I'm eating a ton of carbs all the time and having some wild swings, I'll break out. Ever since I realized those two things, I've had significantly better skin.
As for accutane, it's serious stuff, but holy crap does it work. I'm one of the lucky ones that had absolutely no side effects other than chapped lips. When I was done with it, my skin was 100% clear, and subsequently I never get anywhere near the amount I used to get (but that probably coincides with my original two things as well).