S.P.
Well, this is what my daughter did with my grandson (very high-functioning autistic). He is 4 1/2 now and this was a little over a year ago. He could read. Anyway, first she made him a laminated "book" complete with photos of him and the toilet and a story reminding him that the potty is the place to poop, even when he wanted to play or whatever.... then she made signs which she placed at his eye level all over the main level of the house. They said things like POOP IN THE POTTY, SIT ON THE TOILET TO POOP, POOP GOES IN THE POTTY, and any variation of that, accompanied by drawings of toilets with arrows pointing to the bowl.