The WHEN part has to be when HE is ready, regardless of age. Talk to your pediatrician for signs, but basically dry diapers and then lets you know when he needs to pee or poop (or even if he doesn't specifially let you know, he may have some signs that you pick up on where you find yourself going "oh, he's peeing right now") His body has to be physically ready to be aware that he has to pee, be able to stop the stream of pee before it comes out, and be able to make it to the potty. As for the HOW part of it... I personally think the little potty seats are gross and not a nessesary part of potty training. In fact, I think they are extra work because you have to clean them out and you have to then re-train them to go on the big toilet. I used those coushins that fit on the regular toilet, and a stool so my kids could climb up (with help at first) to the big toilet. I taught my son to pee sitting down first and when he was ready he transitioned into standing (again, with the stool on the big toilet). We always brought a book along, especially for pooping, and we used stickers and MnMs for rewards. I also don't believe Pull UPs are necessary-- they are expensive and I think it hinders the process because the kids really do think of them as diapers. You have to be ready to clean up messes, and you have to have lots and lots of pairs of underwear. Once you feel your child is really, really ready (usually around age 2 1/2 on average), be consistant-- DO NOT flip flop back and forth between diapers and undies. I went cold turkey off of diapers except at night.