I took my daughter to the store and allowed her to pick out her own "big girl undies," whatever design she liked, so she was excited to wear them. I washed them and took a Saturday we didn't have to go anywhere to potty train. I put them on her, explained to her that she would need to go to the bathroom before anything comes out because she is no longer a baby and doesn't need diapers.
First she peed herself and freaked out and cried, she did not like the feeling. I told her calmly that this is what happens if you don't make it to the bathroom in time since these are not like diapers. I put another pair on her and she had the other type of accident in them, really did not like that at all. That was it! Those two accidents were enough, she connected that she did not like that feeling and started getting to the potty on time.
In one day she was completely potty trained. She never even wore diapers to bed, and never had a problem wetting the bed. She was just over 2 years old when I did this. I have found this approach to work with a lot of things with her. If she is able to experience something (in a safe way of course) and see it is not enjoyable or good, she will not want to do it again. I believe in allowing them to make decisions and experience consequences as long as there is no danger in it.