I let the boys take the lead. DS1 showed the first signs of being ready by flushing the toilet whenever he did wee or poo in his nappy. So then we started sitting him on the toilet, and once he understood about doing wee and doing poo, knowing when he had done it, when he needed to do it, and being able to do it on cue when sitting on the toilet, we started underpants. With DS2, he has been sitting on the toilet for a long time now as he copies his brother. I tried him in undies over Christmas and he wet a couple of times and didn't seem interested so I stopped. Then on Friday he asked to wear undies to day care. He has been in them ever since (except for night and day sleeps), and we have only had a couple of accidents.

The first things to do are to talk about wee and poo, tell him when he has done wee or poo, show him what you do and talk about it as you are doing it. Sit him on the toilet at usual "wee" times - 5 - 10 minutes after a sleep, after a meal etc, and praise him when he does something (as well as telling him - you're doing a wee" etc). Once he is regularly able to wee on the toilet (and with any luck poo also), you can try undies.

There really is no magic age, it's just about reading the cues. Also, the ability to pull their own pants off is a handy thing to have mastered before you start with undies. GL.