This article is from the General Cat Care FAQ, posted to rec.pets.cats newsgroup. Maintained by Cindy Tittle Moore with numerous contributions by others.
Cats can be fussy about the cleanliness of their litter box. Many people scoop solid matter out on a daily basis. If a cat is displeased with the litter box for a variety of reasons ranging from cleanliness to the type of litter used, it may well select another spot in your house more to its liking!
Litter boxes are shallow plastic pans. Some cats have a tendency to scatter litter outside the box when they bury their stool. This can be solved by getting a cover for the cat box, commonly available at pet stores. Another way to minimize litter tracking is to put a rug, especially a soft rubber one, just outside the litter box.
For easier litter-changing, some owners will use litter box liners. Some cats rip these while burying their feces; if the problem persists, just don't use liners.
To contain litter tracked outside the box, it is often worthwhile to put the litter pan in a larger shallow cardboard box that will collect most of the litter stuck to the cat's paw pads when it jumps out. Keep the area around the litter box as clean and free from spilled litter as you can. This helps the cat distinguish from outside and inside the litter box. Guess what can happen if this distinction is not clear.
If you have multiple cats you may have to put out several litterboxes. If you have a young cat and a large house, you will either need to place several litterboxes down so that there will be one near enough at any point or you will have to confine the young cat to an area of the house within easy reach of the litter box.
Disinfect the the litter box and top (if any) on a regular basis to prevent illness and disease. Bleach is a good disinfectant around cats, although you should be sure to rinse thoroughly and air out all the fumes. Do NOT use pine-oil based cleaners as these are toxic to cats.