Even though we provided scratching posts of varied types, one of our cats (even though he used all of the posts) wanted to scratch one of the chairs we have.
We bought double-sided sticky tape that is safe for furniture. We left it on for about a week and just sat on other chairs for a while. It was kind of a pain for us, but it worked. After we removed the sticky tape, I guess he'd "learned" that we don't want him scratching the chair. (Cats don't like the feeling of sticky stuff on their paws).
I recently read in a book by a Vet that cats actually like two different types of things to scratch on. We'd read elsewhere that you should provide a good sisal post and that should do it. The idea there was to not get a carpeted scratching post so the cat isn't confused about where it is OK to scratch (the post) and where it isn't (the actual carpet on the floor).
Our kitties scratched the carpet even though we had sisal posts.
The Vet explained it though in a way that makes real sense to me: cats need to do two things. Sharpen their claws, and scratch on something that will remove the dead sheaths from their claws. The sisal is great for sharpening their claws - a loose weave fabric is great for removing the dead sheaths. So I'd suggest getting a carpeted scratching post AND a sisal scratching post. Get posts of varying heights (some come with both sisal and carpet), and get one or two that lay flat on the floor.
The same Vet suggested that when you buy furniture (if you haven't already bought it yet), buy furniture that has a very tight weave. A loose weave fabric will invite scratching, a very tight weave fabric will help to discourage it.
You can also purchase a product called Feliway. It is a spray that mimics the hormone in cat's cheeks. This is a reassuring scent to them, a friendly scent. Supposedly spraying a little on your furniture at cheek height will help prevent them from scratching.
Another common remedy often recommended for use on curtains (to prevent cats climbing them) is lemon-scented air freshener. Cats do not like this smell, and if you spray it once or twice a day on the area you do not want them, it should help keep them from climbing/scratching it.
Also, clip those claws! All of our cats but one are OK with having their claws clipped. We do it about every two weeks. The longer you go inbetween clips, the longer the "quick" (the part with blood in it) grows. If you clip regularly, their claws will remain short. The one cat that minds having his claws clipped gets them done anyway - it just takes hubby to hold him while I clip them.