By nature, the European rabbit (from which the domestic rabbit is descended), never soils its burrow. It chooses one place out away from the burrow where it deposits its urine.
When rabbits live in a human-home environment ("cage" or the special place that they think of as "home"), they bring this same behavior with them. So training a rabbit to use a litter box amounts to putting the litter box where the rabbit chooses to put its urine. :-)
However, it's relatively easy to get the rabbit to use a litter box in its cage by putting it in whichever corner the rabbit chooses to use and keeping the rabbit in the cage for a few days until it is consistently using this box.
To extend the training outside the cage, open the door and let the bunny come out when she chooses to. Limit the space to which she has access to that of a single room and let her out ONLY when you can sit and do nothing but watch.
If the rabbit lifts its tail or heads for a corner, say "No!" in a single, sharp burst of sound (try to imitate the "thump" rabbits make with their hind feet). This triggers the "startle reflex" causing the rabbit to freeze (urinating is postponed) and give its full attention to you.
Gently herd the rabbit back to its cage. Leave the cage door open and let her out whether she has used the box or not. (You aren't trying to force her to urinate, but to learn that when she chooses to do so, she must return to her litterbox.)
Repeat this procedure until she returns to the cage and litter box on her own. Then gradually extend her territory in small increments.
(You can't watch TV or read the paper or knit or talk on the phone and expect to keep your mind on what the bunny is doing every second--if she urinates without being "caught" and herded to the litter box, she'll be that much slower in learning what she's supposed to do.)
(Bunnies take time. Perhaps that's one of their special gifts to us in this hectic world. They require that we take time out to sit and watch and do nothing else. Besides getting a well-trained bunny for your efforts, you also get a short period of time each day to watch one of the most charming little creatures on earth explore, skip for joy, and in general entertain you with her bunny-ness.)
If it is on legs, build a ramp or stairs, or pile boxes to make steps--anything so he can come and go on his own.
If the door is on top, put a small stool or box inside to help him get out, a board or piece of rug to help him walk to the edge of the cage, and a ramp, stairs, stool, or boxes to help him get down (and up again).
If your cage is too small for a litter box, you may have a cage that is too small for your rabbit. (See Section E on the Rabbit's Environment (not yet written).)
Or you may have a dwarf rabbit and can't get a small litter box. A good substitute is a pyrex baking dish. Even 9" x 9" is sufficient for a Netherland Dwarf.
You may have a cage with wire on the bottom and a tray underneath that catches the urine. In this case, the tray is the litter box and the cage itself is where the bunny learns to go.
If you don't use a cage, you need to give the bunny a particular area to call its own. Just put a litter box wherever the bunny seems to prefer.
It depends on what's available in your area and what your rabbit's habits are. Keep in mind the following as you choose your litter:
Pros and cons of the various types of litter include:
A young rabbit may use both the litter and its food dish for both food and litter. However, if you always dump the soiled food out of the dish into the litter box, and clean the dish before more food is given, the rabbit will very quickly catch on.
Rabbits will nibble at the food pellets in the litter box for awhile when they are fresh, but as the litter become soiled, they lose interest.
Finally, some rabbits urinate or drop pills in their dishes as a matter of course. This is not confusion, but a statement to others that "This is MY food dish!"
Dribbles usually indicate a bladder infection. Get your bunny to a rabbit-vet who will probably put her on an antibiotic. If the dribbling stops, you know that that was the problem. (Fear antibiotics given by vets not familiar with rabbits as companion animals!)
If the "dribbles" are more than dribbles, or if the antibiotic doesn't stop the problem, consider any factors that may be making your bunny feel insecure (new pet, house guests, change in location of cage, etc.), any of which can cause a bunny to mark her cage more enthusiastically (similar to someone having a dispute with a neighbor about the location of a fence setting up a flag at the property boundary marker).
When a rabbit is dropping his pills (droppings) all over the house, he's laying claim to it as belonging to him, or at least searching for a place he can call his own.
From the rabbit's perspective, urine is primarily waste material to be depostited in the litter box, but pills are a tool to be used to mark that territory that the rabbit believes it owns.
The trick to getting the rabbit to keep his pills in the cage is to give him ownership of his cage--respect the cage as HIS:
It's a bit like a child going home and closing the door, because someone is calling her names. They may make the playground an unpleasant place for her, but they can't bother her in her own home.
If the rabbit has been snuggling with you, it's okay to carry him to the door of the cage and let him go in--just don't put him directly into the cage, and never chase and trap him and put him in the cage.
The same technique can be used if a rabbit doesn't live in a cage, but in a particular part of a room. Mark the territory with a rug, tape, whatever, and don't trespass over that.