Rascal likes to scratch the couch and a chair. To try to stop it quickly, I bought those "cardboard" couches that you sprinkle catnip on. At first, he didn't know what to do with it. But I took his paws and scratched for him (which he didn't like) but he got the idea. As soon as he started scratching it on his own, I praised him. Everytime he uses it, I praise him.

Of course, I have little pieces of cardboard around the area, but it beats having him using the sofa or chair. He also sleeps on the sofa for long periods of time. Every once in a while he has a lapse, but if I can catch him, I will yell NO very loudly and he will stop. Then I take him back to the cardboard couches (if I can catch him).