My daughter just mastered the whole thing at 3 years 9 months.
(This is a very smart little girl. But one who is amazingly stubborn and has a baby fetish. She doesn't want to be a "big girl" and is much happier as mommy's baby).
We tried stickers, m&ms and peeing for presents. We tried vinyl training pants and just letting her run around naked. We promised her a cruise and a trip to Disney (I knew I'd promised too much when my four year old told her "Mommy will buy you a yellow bug car (a VW Beetle) if you potty train"). We put her on the potty every half hour. We didn't bug her once for two weeks. We sang songs, watched potty movies, pushed peer pressure, We tried EVERYTHING.
You can't potty train a child - they need to decide its time. You just get to provide the motivation and instructions. If you get lucky and stickers work, its because your kid decided it was time (and stickers helped motivate). Its always the last thing that works.
I took her to the peditrician for pink eye and her doctor talked to her and set some rules. Only big girls wear underwear. Babies wear diapers - not pull ups but diapers. If she went potty she could wear underwear, but if she had an accident, it was back to a diaper until SHE decided to put the underwear back on. At the same time, Mom started talking about how she really didn't LIKE babies. We avoided babies. I didn't hold babies if my friends brought them over. I praised the big kids in the neighborhood and talked about how much fun I had with them.
We went through half a pack of diapers and it took about two weeks. But she did it. Boy did she throw a fit when the diapers went back on. Now whether the incentive was what did it, or it was time, or it was a combination of things, it was done.
So now I'm over here because NOW I feel I can start exploring the
Disney cruise. Didn't want to do it until she was potty trained.