yeah with my first I started with him before he was two, spend tons of time and money on all sorts of treats, games, prizes, stickers, bullseyes... It went back and forth. First he would get the poo in the potty okay... then he would get the pee right (but not the poo). Back and forth. We went on vacation a few times and he finally was potty trained, or so I thought, but then we'd get back home and I'd discover nasty poo on the ground in the middle of the living room. He finally got it when he was about 3... I really think it's because HE was ready. Then we kept the pull up on during nights for about 4-5 more months, and after that he didn't need anything at night (but I would put waterproof bed sheets under the mattress just in case for a while - you know the ones older people would use).
As for the best potty seat cover (in response to Anthony's Mommy's post), this is it: The Best Potty Seat Trainer
(it's the bjorn potty seat trainer and it's amazing b/c it does not shift, and it fits perfectly making it seem like it's part of the bigger potty!)