1. Make sure the litter box is cleaned daily. Your cat will start using other places if the litter box is too dirty.
2. If you have recently changed brands of litter, try changing back. Cats can be picky.
3. If your cat has just been declawed, their paws may hurt when they dig in the litter. Try adding some shredded shiny newspaper on top of their regular litter. The shiny newspaper cushions their paws and will not stick to their sensitive paws.
4. Put the litter box and your cat in a small room, like a bathroom. Make sure he has plenty of food and water. Check on your cat once an hour. If the cat has eliminated correctly in the box, praise the cat and let them out for some supervised playtime, or give them a treat. Then put them back in the room. Repeat two or three times until it seems that your cat has "gotten it".
5. If the cat misses the box, place the feces in the litterbox and do not pay further attention to the cat. Leave the room and check again in an hour.
6. If your cat is still avoiding the litterbox, take him to the vet to make sure there is no underlying medical reason for this behavior. Urinary infections, kidney problems or parasites (worms) can be reasons the cat is not using the litterbox.
7. Also think of any reasons that there may be some behavioral issues that may cause the cat to 'act up' such as adding another animal or person in the house, changing routines, moving the box to a new location, noise or light changes.. all can be signals that your cat is stressed. A checkup and a discussion with your vet will be helpful to you and your cat!