We used a reward board w/ stickers and a prize after so many stickers. We've also tired jelly beans as rewards. My daughter was just under 2 when she started to "self train," but in the middle of it her little brother was born and since he wears diapers... Fast forward to today, she just turned 3 and we're still not 100% potty trained. She knows how to go and can do so on her own, including wiping, flushing, washing her hands, etc. but just choses not to sometimes.
Our greatest success recently has come from one of her friends that's potty trained. It's almost become a competition between them to see who can go longer w/o an accident. Who says peer pressure is a bad thing