Christine-
My sons are 25 months apart and the oldest started showing a high degree of interest right before the second was born, but I decided to wait because I didn't want to hurt his progress because I was busy with the baby when he needed me. We did go full force with him when he was less than 2 1/2 and he was fully trained (night, too) in less than 3 days. I can tell you what I did... First of all, buy your son underwear that he is excited about and then on the day that you are ready to start, hide the diapers out of sight and put his underwear on him with a speech on what a big boy he is. You WILL have accidents, so be prepared to clean those up. When he does have one, tell him that it's okay, give him some support and encourage him to make it to the potty next time. After an accident or two, he will start to go in his underwear, but the wet feeling will remind him and he will finish in the potty. It's all about breaking the habit of just going when he has to go. Every hour or so, take him to the potty and have him try, and try not to get frustrated when he has an accident 2 minutes after you take him; it will happen. As his accidents get more seldom, you can remind him to go less frequently. You'll be able to tell how he is adjusting. As for nap time and nights, but a pull up on OVER his underwear. This won't confuse him, he'll still have the feeling of his underwear next to his body, so he should be able to tell you if he feels wet, but it will protect your sheets. Also, on your first outing or two, don't be afraid to put a pull up on over his underwear, also, but also take him to use the restroom while you are out. Whatever you do, don't go back to diapers. It will only confuse him. If he is showing interest, he is ready, it is just a matter of breaking him of the habit. Good luck!