What solution do you find best for kittens or cats that scratch?

Yes, declawing has so many negatives - and it's totally unnecessary. The best thing to do is provide multiple scratching options. The best one is a nice sturdy piece of cat furniture with both carpet and sisal. Cats tend to want to S-T-R-E-T-C-H when they scratch, so the post must be both tall and heavy so they can get a good stretch. Also provide a cardboard scratch box, most cats (kittens especially) love them, especially the "inclined" ones. I've fostered many, many kittens and all of them left to go home knowing that the cat trees and cardboard things were for scratching, and none of them scratched the furniture or carpet inappropriately.