S.F.
I tried stickers with my oldest son, now 4, and that seemed to work great. I bought like 100 little stickers in an assorted pack. My son loves sports, so I let him pick out a sticker for each step in the process, pee, poo, wipe, flush, pull up underwear, pull up pants. He loved stickers, so I would let him know he could have some stickers if he went on the potty. After he got used to sitting, then I would only give him a sticker if he pee or poo on the potty. Then it became only if he went to the potty and pulled up his own clothes on his own.
My younger son, now 3, took more work. We tried stickers and going outside, going to the park, picking what he wanted for dinner, etc. We finally ended up resorting to candy. He would get a tiny chocolate if he went pee and a sucker if he went poo. Getting him to pee was easier than poo. Since he liked hard candy more than chocolate, we gave him the sucker for poo.
Sometimes he misses or doesn't make it on time, but I still reward him as long as he tried. He missed at daycare, and daycare put a pull-up on him. For about 2 weeks he kept going in his pants because he wanted to be a baby and wear a pull-up again. Since he was being defiant, I needed to try something different. Finally, I put him in timeout for going in his pants, and now he goes in the potty pretty much all the time.
We backed off the stickers and candy since they are both consistent, but a couple times a week I reward them for going potty with stickers, sucker, a special outing to the park or something like that.