Here's an article on scratching that was in Cat Fancy recently.
A Scratching Outlet
Giving your cat a place to scratch early on may help prevent household damage.
Scratching has a variety of functions for cats, the most important of which is marking territory. Other possible functions include claw maintenance, stretching muscles and tendons and play, especially in kittens. Because scratching is such an important behavior, it is not realistic to prevent a cat from scratching. Instead, cats need to be encouraged to scratch items meant for them and to leave furniture and other household items alone.

Cats tend to develop preferred scratching locations to which they return repeatedly. Thus, it will be easier if from the first day as many objects with potential "scratch appeal" are made temporarily unappealing while acceptable scratching items are made available and attractive. The arms and backs of furniture can be covered with plastic, and drapes can be scented with deodorizing sprays with strong floral or citrus odors that cats find unpleasant. The kitten can also be confined away from tempting items when left unsupervised for short periods.

Just as cats develop location and surface preferences for elimination based partially on early experience, they also have individual preferences for where and what they like to scratch. You may want to provide several different types of objects initially to see what the kitten prefers. Try at least one vertical object, such as a post, and one horizontal one, such as a cardboard scratching box. Place these objects where the cat is most likely to be motivated to scratch, such as near its bed, near the front or back door or in an area where the kitten plays. Your cat may use more than one scratching object regularly.

Styles are available to fit any budget, from a simple cardboard scratcher to an elaborate 6-foot tree. Some are covered with carpet only, while others have sisal in the scratching areas, which helps extend the life of the post. Specialty manufacturers make designs with natural wood or carpet fashioned into palm trees, airplanes or other forms that make great conversation pieces.

Scenting scratching objects with catnip or attaching a toy on a spring to the top of a post will encourage most cats to begin using them. Some cats will be enticed to scratch by the sound of you scratching the object. Taking the cat to the scratching object and moving its legs up and down is not recommended. The cat will not associate this action with its natural scratching habits.