DS4 got a complex at some point about the toilet and wouldn't have anything to do with kiddie potties or toilets. There was no incentive that would actually make him sit there.
So we started by having him pee in the tub/shower, at least that was in the right room. He went anyways upon being put in a filled bathtub, so it wasn't a big transition to a tub with no water in it. Once he was comfortable with the holding it, running to the tub (initially being lifted into it and then later peeing from over the side as if it was a giant toilet), parent rinsing it after (flushing), etc, then he was used to peeing only in the bathroom. After that it wasn't so hard to transition to (standing up on a stool) peeing into a potty/toilet without actually touching it. Then after that was easy, we tackled pooping. That way the actual sitting on a big scary hole was one of the last things he had to do and came after he was fully comfortable with all the other aspects.
Polly
