Cats who urinate outside their litter boxes may be suffering from health problems, so rule that out while breaking your cat of this unpleasant habit. Bladder or urinary tract infections, diabetes and incontinence can all lead to Fluffy eliminating outside of the litter box.
Clean the litter box out every day, and completely empty it once a week. While it is empty, wash it with an unscented soap or baking soda.
Measure the amount of litter you put in the box. You don't need to break out the ruler, but overfilling the litter box is a common problem, and can cause your cat to look elsewhere to do his business. One to two inches of litter is ideal.
Move food and water dishes away from the litter. Your cat doesn't want to eat and use the bathroom in the same spot, so, since he can't move his dishes, he may change the location of where he goes to the bathroom.
Provide plenty of room for him to go to the bathroom. You may need more than one box in different areas of the home. This is particularly important if you have more than one cat. You may also need larger boxes. If your cat doesn't seem comfortable in a standard sized box, use a plastic storage bin without the lid.
Use an enzymatic cleaner to clean up any accidents. If your cat can smell urine, he will return there to eliminate.
Keep your cat off areas where he likes to eliminate. Once your cat develops the habit of going outside of the litter box, it can be a real challenge to get him to leave certain areas alone. If he has specific spots he keeps returning to, place foil or double-sided tape down to cover the floor in that area.