A.,
There are lots of different ways to go about potty training. It's great that he tells you when he has gone. I have three boys, 4, 2, and 8 months. My four year old started training just before he turned two. He was really into it, then stopped. He is finally doing it consistantly, although he does still have an occasional accident, sometimes.
We used a potty chair with him in the beginning. He seemed to like it. But he did better once we put him on the big potty. He would sit on it (kind of like a girl would) and go.
My two year old is still in diapers, but does use the potty sometimes. I really thought he'd be doing better since he likes to do everything his big brother does.
We used a sticker chart for a while. I taped a piece of paper on the mirror in the bathroom, with rows and columns. Everytime they used the potty and washed their hands, they put a sticker in a square. We also did little treats. (We still use them now) After they finish, and wash hands, they get two gummy bears. (We started with, three, and just went down to two)
Whatever you do, don't pressure him, and don't get mad if he takes a long time to go. Sometimes I think I rushed my oldest too much, and maybe that's why he stopped going. It can be very frustrating to potty train when you have another little one around that also needs attention! Ask him if he has to go, and occasionally put him on the potty. Some kids like to be left alone, some don't. It takes a lot of trial and error. Good luck to you. I have often heard that boys take a lot longer than girls. But once he is really ready, it shouldn't take long!
Best of luck!
G.