I started my son in earnest about a month ago (he is now 2 yrs, 2 mos old). All the books and people are very adamant about not starting training until the child is ready, but how the hell do you know if they're ready?
There are a few signs:
- the child expresses genuine interest
- longer periods without urinating, such as through a two-hour nap (hard to know, but you can try testing this by putting on a clean diaper before a nap)
- regularity for #2s (like always early morning and almost always around 5 pm)
Many books will offer more signs of readiness.
In retrospect we probably started a month or two early, but his pals at "school" were using the potty, and one day he refused to put his diaper back on, so I figured we were committed.
At school (3 days/wk) he now has no accidents during the day. At home he has a few. I put this down to the fact that every time any kid walks by a teacher at school, they slam them on the potty. His teachers belong to the camp that believes if a kid gets wet over and over again, eventually the light bulb will go on and s/he will announce the need in advance.
At home I am often doing something else or lose track of time (45 minutes is about the max between visits), so he has more accidents at home, but these are becoming less frequent by the week.
At other people's houses, whether I am there or not (grandma's, visiting at friends' houses), he often does not get to the potty in time. I figure he is a bit apprehensive about asking to go in the presence of others, or he is simply in less familiar surroundings.
At naptimes sometimes he wears a pull-up, sometimes just underwear. Overnights is still a regular diaper.
Like everything else, this is a process. It is taking longer than I wanted, but his improvements are noticeable from week to week. Patience is key, and sticking to it probably even more important.
Summer is better to be dealing with this in winter -- pants off the whole day if possible, inside and out, when you are at home.
And once they start announcing, you cannot let them fail, even if you have to pull over in the car and let them do their business on the side of the road -- have plastic bags and wipes at the ready!
Good luck.