There are lots of ways to discourage clawing. First and foremost (since you didn't mention it we're all going to suggest it), he needs some kind of acceptable outlet for his clawing. Like Hissy said, they need it to stretch their muscles and also to remove dead layers of claw. Sisal scratching posts are great, but you will probably either have to order or build a good tall one. The ones that I have seen at Petsmart and Petco just aren't tall enough for a grown cat. They have to be able to stretch their full length. They do have some flat ones that hang from a doorknob that work well and are tall enough, for about $15. My cats also love the cardboard scratchers that are flat and sit on the floor. They took to those immediately, and they are only $5 or $10 for the doublewide.
Most cats don't like citrus at all. Since he is scratching wood, clean it really good with a citrus scented wood cleaner. Really penetrate the wood with that citrus smell. Double sided tape, like Laurie mentioned, usually works well. It won't look good, but most cats also don't like how aluminum foil feels on their paws. You could put that on the floor in front of where he likes to scratch.
Positive reinforcement works the best to train cats. They don't respond to punishment, they just associate you with something bad. Once you have a scratching post/thing for him, whenever you see him scratching something he isn't supposed to, just pick him up and put him by his scratcher. You may even show him what he's supposed to do with his paws. When you see him using his scratcher, praise him to high heaven and maybe even give him treats (if he's treat motivated) for using it.
If all else fails, check into Soft Paws, which are the nail tips Laurie mentioned. You can have the vet put them on him, at least until you feel comfortable enough to do it yourself. Declawing really is as horrible as the stories you have heard. It is amputating the first knuckle, and very serious health and behaviour problems can result from this procedure. It is banned in many countries as cruel.