Four things to consider when setting up a litter box
Cats eliminate to fulfill a fundamental need and also to mark their territory. You can help ensure that your cat doesn't feel the need to use eliminations to announce that your home is their territory by providing an attractive litter box. The goal is to provide your cat with a positive experience when using the litter box. If your cat has a negative experience while using the litter box, they will avoid that box in the future.
Cats are fastidiously clean. Most cats avoid using a dirty litter box in favor of a cleaner place. This may be your bed. To prevent house-soiling, the litter box should be scooped daily and washed weekly with mild dish detergent. It's also recommended that you purchase new litter boxes every six months because the scratches that develop in the bottom of the box can trap urine odors.
-Type and Size
Cats generally prefer large, uncovered litter boxes. Uncovered litter boxes are more easily accessible to your cat. Larger boxes are better because they provide more room for your cat to move around. As a rule, the litter box should be large enough for your cat to stand up (on all fours) and turn around in.
There are many different litters on the market. Research has shown that most cats prefer fine-grained, unscented litter. Scoopable litter usually has finer grains than typical clay litter and is easier to keep clean on a daily basis. Many cats don't like scented or deodorant litters. Once you find a brand of litter your cat likes, don't switch or your cat may refuse to use the litter box. If you do need to change, the cat should be offered the new litter in a box placed next to the old box. This allows the cat to decide if she wants to use the new litter.
-Location and Number
Cats like quiet and privacy when using their litter box. Place boxes away from appliances or air ducts that could suddenly come on and startle the cat. They should also be placed so that humans and other animals can't "sneak up" on the cat. Make litter boxes accessible. Don't place them in "tight spots" such as under sinks or low tables. Also, in homes with more than one story, litter boxers should be available on each level of the home. Cats are lazy and don't like to walk far to get to the nearest litter box.
The Golden Rule is one litter box per cat, plus one. Each cat requires its own place to eliminate and mark it's territory.