I am just starting with my daughter who just turned 2 and I know the one thing that you can't do is put pressure on them. I have just been taking her in there once every hour or so to try. We have fun things in there for her to do while she's on the potty, like reading books (they even have potty books that talk about going potty....we have a Dora one and another one and she loves them both....they even have buttons on them that make a flushing sound) and writing on her mini Aquadoodle pages. She gets a sticker when she goes and is starting to catch on. My daughter is very verbal and way ahead of the curve (developmentally, she is at least 36 months verbally according to her pedi), but I have to remind myself that just because she is smart doesn't mean she is going to be potty trained overnight. She has been sitting on the potty for 6 months or so without any real success...she just thought it was fun. Now that we're really focusing on it, she is starting to understand, but it is taking some time. She still doesn't know to tell me when she needs to go and doesn't tell me if she's dirty, so we're going to be working on that, but she is at least starting to recognize what it feels like to go and once she has that awareness down, I think it will continue to help. Sorry I rambled.
The bottom line is that this isn't easy and they have to be interested if it's going to be successful. You can't force them...it will just stress you both out. Just offer incentives and fun things to do while she's sitting there and try to keep her interest up. If she doesn't show any interest, take a break for a month or so and try again.