2. Move the litter box onto the toilet seat. (For kittens or new kitties, you can start at this step.)
Begin decreasing the amount of litter until it's nearly nil. Next comes the tricky part ...
3. Fashion a kitty training seat from wax paper or an aluminum pan, tape it underneath your toilet seat and add a scoop of litter and a sprinkling of catnip.
Be sure to adhere to the toilet seat itself - versus the porcelain brim - so it's less of a pain when you need to go! (If you ain't got time to D.I.Y., you can purchase a cat training seat here.) Clean frequently, and gradually reduce litter.