Most kittens are eager to learn how to please you. You can easily correct behavior in a young cat with a gentle but firm tone and a demonstration of the proper way to do things. Praise your kitten when you point out the litter box and scratching post.
Depending upon how happy and peaceful their former lives were, older cats may be a little more difficult to teach, but they are well worth the effort. Patience and kindness, with perhaps a firmer tone of voice, should help maintain most ground rules. Hitting your pet is cruel and accomplishes nothing—it will only teach your cat to be afraid of you. A good discipline tool is a spray bottle filled with water. Catch the cat in the act of scratching the sofa or jumping on the sink and spritz the culprit with a gentle spray of water. Your cat will associate the behavior with the unpleasant experience of water, but will not associate you with the unpleasant experience. Source: Fact Monster