I used the book "Toilet Training in Less than a Day" and it worked AMAZING for my son! I got it from a recommendation on here. The first step is to get a doll that pees and have them help you teach the doll to do it (everything from pulling underwear up and down to emptying the potty chair), and if the doll stays dry, they get a treat. Show them how it works with the doll first. I got a boy doll called Gotz Aquini, and gave it to my son for christmas. I got it on Ebay, but saw it at TJ Maxx this week for about $12. It includes a potty chair, underwear, and a bottle to feed it.
That part can be skipped if you want... we actually didn't really end up doing it. But it also says to give them salty snacks instead of sugar... makes them more thirsty. And anything they will drink. For the only time in his life my son got pop and kool-aid. I gave him a full weekend at home, with my full attention. I didn't worry too much about eating his meals for that weekend, I worried more about what would help make it less stressfull. He had Frito's, every few minutes if he was dry, he would get one. If he went potty (he prefers standing, and the toild over the potty chair. he is short... so he needs a foot stool.) he gets a handfull of frito's. If he was wet, he had to change his underwear himself and learned it was easier to just go potty. If he had an accident and then used the toilet, he would only get one frito. He filled himself up on frito's that weekend and didn't eat much else, but it was only for about a day. Every time he would try, I would tell him how happy mommy is that he is a big boy (because diapers are for babies and underwear is for big boys), and I would list off everyone else he cares about and how happy it makes them, and he got really excited. He will still say "Mommy's so happy!" sometimes after going potty, and is so proud that he can do something that makes mommy happy. I did not use pull ups at all... not even for sleeping. He has always had dry diapers in the mornings though, so i wasn't too worried. His first day went really bad... he seemed to have no control and I was ready to give up. I kept it positive the whole time and didn't show my frustration... but I was going to give up. The 2nd day he woke up, went potty right away, and did great the whole day. He had once accident right before bed, but that was it for the whole day. And he has done great ever since. That was the first weekend in January. He has accidents sometimes at daycare, but never at home. I think part of the reason, is that at home I have taught him to go completely independantly, I don't even go in the bathroom half the time. He does it all himself. At daycare, he has to wait for them to take him, and I think that is why he has accidents there.
I would recommend getting and reading that book.... I didn't follow everything, but got a lot of good ideas. They tested it on 200 children between 21 months and 4 years, and almost every one of them got it. The longest one was 2 days (7 hours each day). Only 2 were not successful, and both of their fathers did not think they were ready to potty train and were not supportive.
Also, the best advice I have heard is no pull-ups. Just put him in underwear, and let him learn it isn't comfortable. Pull-ups don't teach anything, and can delay the potty training months because they are still comfortable if they have an accident. I put my son in underwear on Jan 7th, and haven't put him back at all. Every once in a while if we have a late night and he is asleep before we get home, I put a diaper on him at bedtime if he doesn't wake up to go potty. But other than that... he has been in underwear, and very proud of it. I bought all of his favorite cartoon characters (spider man, jojo's circus, wiggles, and mostly elmo... and he gets very excited getting to choose which ones he wants to wear.
Good luck!