First let me say "Good Luck". My son is almost 4 (15th) and he's still working on it.
The Dr. said boys tend to be closer to age 4. (my daughter was completely out of diapers even at night by 3)
Other Moms say boys are lazy and will do it when they're ready.
Some say leave them naked over the summer and that makes them more aware. Or give him lots of drinks so he'll have to pee more and that will make him more aware.
Maybe have a bye bye diapers party (throw them away)
Mostly It'll depend on him.
I do rewards. 1 jelly bean for pee and 2 for poo, as well as a star on the calendar so he can see how well he's doing. We have the "Sean went pee pee on the potty" song and dance. And we clean up the messes. (our big prob. is #2) We've also watched the "Potty Song" for boys DVD and having his father show him. Boys want to be like Dad... I've tried leaving him naked from the waist down and it did work. However with him as soon as I put clothes on him he figured that he must have diapers on and peed right through many times. Try starting at bringing him every 15 - 20 min to the potty and slowly increase the time. Some kids will get tired of you making them try that they'll start tell you when it's time. (not mine unfort.)
I've heard the peer presure will work also.
Try different things and see what works best for you and him.
Good luck!!!! Every day is a new begining for making progress.
H.