My last kitty (R.I.P.
) was NOTORIOUS for scratching on my couch. Here's what worked for me that got him to break that habit...
1. Buy a scratching post! As soon as I got him one, he left my furniture alone.
2. Squirt bottle. On those ocassion then I would catch him getting ready to do it on my furniture. After a few squirts, he left the furniture alone and just used the scratching post.
3. Clip his nails. I kept my kitty's nails clipped because those things do get sharp. They sell kitty clippers for about $3-$5 bucks everywhere (pet store, Wal-mart, etc.)
I'd thought about getting him declawed, but didn't, mainly because I'm cheap.