The very most important thing to remember is: Lid Up, Seat Down.  Post a note on the back of the door or the lid of the toilet if you think you (or your housemates or guests) might forget. ( Nowadays, if I have a guest who leaves the lid down, Misha will usually come and ask me to fix it, but you can't expect every cat to go to this much trouble.  Besides, he's been using the toilet for more than six years now; when the whole idea was new to him he'd just as soon pee in the bathtub instead.)  And if you are accustomed to closing the bathroom door when it's empty, you'll have to break that habit too.  From The "How to toilet-train you cat" web site