The best way to prevent kitties from damaging your valuable furniture is to provide them with something valuable to them -- a fancy scratch post or board. Cats like durable objects with certain textures more than they like your new furniture. Give them a better scratch device and they'll choose it over your couch.
Cats need to climb and be animals. Make sure your home offers your cat opportunities to be the hunter it is. Does it have enough toys, ledges and climbing spots? Before you blame your cat for ruining your furniture, check to see that you have enough to entertain it.
If your cat is scratching a specific spot time and time again, try covering that area with a blanket or thick towel. If you limit access to the spot, your cat will likely back off. If your cat needs more guidance, try double-sided tape for a while. It's not pretty, but it does the job. Certain fabrics also deter cats from scratching. Microfiber is known to be scratch-resistant.
If your cat still wants to scratch, try a product called Soft Paws, which are nail caps for cats. These are vinyl caps that fit over your cat's claws to prevent scratching. As a bonus, they come in a variety of colors -- fashionable and functional!
Try not to punish your cat for scratching your new couch. Punishment may keep your cat from scratching while you're around, but it won't keep your cat from scratching when you're not around.
Finally, talk to your vet before you completely give up. Often, destructive behaviors lead people to give up their animals. There may be solutions that your vet can offer. Try all of your options before you throw in the towel