I gave my DD lots of nudie time and just didn't put her back into nappies. One day (a planned day) we got up and the nappies were never to go on again. This was at 22 months, but I am pretty sure she could have done it earlier anyway because for us it was a matter of me being committed to taking her to the toilet all the time. I also used diluted lemonade as a treat for the first few days to make sure she got lots of fluid and lots of opportunities to try. Then when she did a wee on the toilet she got a star sticker on her chart! Very exciting. Though sometimes lollies were a better bribe!