Probably no single factor contribute more to the owner's happiness than a rabbit that is trained to use a litter box. The ease of this task will depend primarily upon three things; the age of your rabbit, whether or not the rabbit has been altered, and how many rabbits are in your household.
Very young rabbits are forgetful, unaltered adult rabbits of both sexes spray urine, and rabbits in multi-rabbit households leave more territorial droppings.
If your rabbit is only 6-8 weeks old, you may as well resign yourself to many "accidents." Young rabbits require more repetitions to learn the task than older rabbits.
If you have a little baby bunny, begin the process of litter-training him by noticing which corner of his cage your rabbit tends to use to urinate in. Move the litter box to that corner if it is a different one than where you had placed it. When you let your rabbit out of the cage, place him in the room litter box immediately. If he urinates in it, praise him. Continue to place him in the litter box about every 5 minutes during the time he is out. If you notice him backing up and lifting his tail when he is not in the box, lift him immediately and place him in the litter.
Be prepared, however, very young rabbits forget quickly as they learn. It is easier to train the rabbit to urinate in the litter box than to leave all his droppings in it. A rabbit will probably always leave a few scattered territorial droppings around your house. They can be trained to leave the majority of them in their box, however. Rabbits in the wild have "latrines" where they leave most of their droppings. Your house rabbit simply needs to learn that his litter box is his latrine. Most rabbits will figure this out on their own, but if yours has difficulty, sweep up his droppings and put them in the box.
For a short time, you will think that your rabbit is wonderfully trained, and then between 5 and 7 months of age when he or she reaches sexual maturity, the rabbit will often revert to his previous unacceptable habits, and display a few new ones. Both bucks and does may spray urine if they are not altered. The difference between an unaltered and altered rabbit can be quite dramatic. Spraying urine is actually a sign of affection in rabbits! Altered males usually stop spraying urine within a week after the procedure.
Training an adult male that has been altered to use a litter box is similar to teaching a young rabbit, but will proceed faster. Once your rabbit starts using it on his own, the key to keeping his good litter box habit is to keep the litter box clean. Remove the soiled litter once a day, and clean the box thoroughly once a week. Another key to having a rabbit with good litter box habits is to provide enough litter boxes. The more space your rabbit has to roam in, the more boxes you will need to place in strategic corners throughout the house.
However, if you have a multi-rabbit household, litter training will be more difficult.
Rabbits eliminate a special kind of droppings a few hours after they eat. Called "night" droppings because people rarely see them and because it used to be thought they were eliminated primarily during the night, they are soft, smelly droppings often in a grape-like cluster. In order to obtain needed nutrients, rabbits consume the majority of their night droppings, a behavior called coprophagy. This may seem gross to humans, and we may grimace and say "Yuck!" if we see our rabbits eating them. Please, do not attempt to stop your rabbit from consuming these droppings or punish him for it. Rabbits must eat these droppings to remain healthy.