Scratching is a natural behavior for cats and any means of punishment will not stop them from doing it.  It's an instinctive behavior because it's a means that cats can use to mark their territory.  Cats have scent glands in their paws.    

My personal opinion is that cats come with claws and if you own leather furniture, get rid of it! I love my cats and simply put, they are more important than owning leather furniture!    

Regularly clip your cats claws.  If you are afraid to do this, then have someone show you how.  It's really very simple.  You just use nail clippers that are made for cats, apply a little pressure to the toe to get the claw extended, and then just clip the very end of the nail, avoiding the "quick."  The quick is the pink part of the nail.  If you accidentally cut the quick, put some Kwik Stop on it to stop the bleeding.    

Offer your cat a scratching post or pad that he likes.  Carpeted scratching posts have never appealed to any of my cats.  The type of scratching posts that appeal to my cats are the poles that are wrapped with sisal rope.  Several, however, prefer the corrugated cardboard pads that I sprinkle catnip into.  They go nuts!  I have several "Cat Tracks" toys where a corrugated cardboard pad is in the center and is replaceable as it wears out.  Cat Tracks are great.  My cats really like and use them.    

A common problem that I experience is having my eight-week old kittens mistake my legs for trees and climb my blue-jeans to get into my lap.  They outgrow this behavior very quickly with discouragement.   If you buy a sisal pole with a perching area on the top, you can place some treats up there for the kittens.  This will encourage them to go there  to climb.  They also use the many "cat furniture trees" that I have in the cattery patio area to climb.    

I've read that if your cat has been scratching the furniture you can cover it with double-sided carpet tape to protect it.  You can also spray the areas with a product called Stainaway that removes the cats scent.  Then encourage your cat to use the sisal pole, or corrugated cardboard pad by using catnip to lure him to it.    

My kittens learn very early from watching their mothers use the scratching posts and corrugated cardboard pads that this is where they are suppose to scratch.  This should make them better pets for you.    

Here is the CFA's position of the declawing of cats:    

"The Cat Fanciers' Association recognizes that scratching is a natural behavior of cats and that cats may be defenseless without full use of their claws if they, either intentionally or unintentionally, go outdoors. Scratching damage to household furnishings can be minimized or avoided by routine clipping of the claws, the use of claw covers and by redirecting the cat's activity to acceptable surfaces.    

CFA perceives the declawing of cats (onychectomy ) and the severing of digital tendons (tendonectomy) to be elective surgical procedures which are without benefit to the cat. Because of post operative discomfort or pain, and potential future behavioral or physical effects, CFA disapproves of declawing or tendonectomy surgery."