The more signs your childs shows, the quicker he will learn. BUT you can start anytime you want. From what I've read, a child will be potty trained at the same age, regardless of when you start. If you start at 12 months because you want to but he won't be ready to learn until 30 months, you'll be training for 18 months. If you start at 27 months because he's showing lots of the signs, then you'll be done at 30 months after training for 3.
Also, once you start, expect him to get it one day and not the next. Regression is normal and to be expected. Do not ever ask him if he needs to go. Simply tell him it is time to go. Kids quickly learn that saying "yes" means they have to leave their toys so they learn to say "no". Accidents because a child was too busy playing are common into early grade school.
at 3:34 PM on Feb. 26, 2009