Summarize this article:

The most effective way to keep your home from smelling like cat urine is to prevent spraying in the first place. One of the best ways to do that is to make sure that your cat is happy with his litter box situation. Cats are very particular about their bathroom needs.  If your cat is spraying, ask yourself if his box is clean enough. You may need to change the litter more often and scoop the box more frequently. If your cat started spraying after you switched litters, he may not like the new brand. Try a new product to see if he reacts more favorably to a different kind of litter. Consider getting another litter box. If space allows, give your cat another option for elimination. This may reduce his desire to go elsewhere. Most cats who spray are  males who have not been neutered. It is a way to mark territory. If your cat has not been neutered, ask your vet about the procedure. It will likely stop the spraying.  Cats may spray because of health issues. If this behavior is unusual for your cat, consult your vet to see if there is an underlying problem. Cats often spray because of stress or anxiety. For example, if you have recently moved or introduced a new pet into the home, your cat might react by spraying. Try to give your cat some extra affection. If the cause of anxiety isn't immediately evident, ask yourself some questions. Has your cat's routine changed? Is it possible that he is being bullied by another cat in the neighborhood?
Clean the litter box. Monitor your cat's health. Provide a stable home environment.