At 37mos, my son's first day was me taking him every 20-30mins while cutting back his water intake (he loooooves water and would easily drink 40oz before lunch). We went thru all 20 pairs of underwear. The second day, he got sick of always having to go, so marshmallows were introduced as incentive, we went thru about 16 pairs. The third day he decreased his water intake on his own, was fascinated by the poop "shooting out" into the toilet and did so well, we left the house for an hour w/out an accident. He also got sick of marshmallows, so we went to Tootsie Rolls.
By the start of the second week, he was SO much better at determining when he needed to stop what he was doing. He had 1 accident at a play center, which was my fault because I was 2mins late in getting to him to take him to the bathroom. We introduced the 'trunk potty' and he got a Hershey Kiss whenever he used it. He was down to 2 pairs/day and no other treats/incentives.
By the third week, he was in control about 95% of the time, determining when he was going to go. I had to prompt him maybe once or twice during the day, but it seemed to have 'clicked'. And he was waking up from naps dry. There were a few days in between those 3wks where he would only pee enough to kind of take the edge off, and I had to come up with creative ways to keep him on (counting to see if he could pee longer than before, introducing new interactive books, etc). He was down to 1pair/day.
At 28mos, my son insisted on no more diapers - he'd been peeing in the potty before bathtime for almost a year, he'd been watching his friends go potty and sometimes being their cheerleaders. We tried it, but his water intake was causing him to go every 15mins and he was ready for the diapers after 2 days. I figured I'd just wait until he was 3yo, until the summer/warmer climate with less clothes, and earnestly try then. It seems to be working, but I don't want to jinx myself :)
Also, he didn't always need changed because of an accident - I changed him any time there was wetness, maybe from him grabbing 'it' so much, maybe from a drop falling when he stood up from the potty.
I also followed other moms' advice by never asking him "do you want to go potty?", but by just directing him "its time to go potty".
Good luck!