So....WHY DO cats scratch? It is an innate behavior of cats. It is as essential as breathing, a behavior with which they are born. Scratching not only manicures kitty's nails into fine condition, but helps them to visually proclaim a territory as theirs while also leaving a scent marker behind (their visual and olfactory personal calling card). Cats also get a fantastic stretch of their front legs and shoulders and toes when they scratch! Perhaps you adopted a kitty that was already declawed and have seen them continue this process. Many people think cats are silly to do so or too "stupid" to realize they no longer have claws (Have no doubt, they do know it), but they continue for the reasons stated above...it is part of what makes them cats.
This innate need too often conflicts with our expectations of how cats should behave in our homes. However, understanding this innate need prepares us to provide the resources cats require and allows us to happily co-exist with them. Furnishing proper scratchers throughout the home is key. There are additional efforts we can make to eliminate damage from their claws as well.
Because your entire home is also your kitty's territory, you will need more than one scratcher. If you have several cats, you will definitely need more than one! Hopefully you have at least one cat tower/tree in your home and it has good scratching material for kitty to use. If not, get one...or two or more. Cats like to be in high places to feel safe and watch their surroundings. A family room, your bedroom, etc., are areas cats prefer. They can have their "own furniture" and still be with you. Similarly, scratching posts should be located throughout the home.
There are many materials offered on the market for scratching. "Floor carpet" wrapped are liked by many cats, but those are not recommended. Should kitty decide it's the favored material, there could be issues with cats scratching floor carpeting in future. Best not to get kitty used to that! Other materials are wood, indoor/outdoor flat carpet (very durable), sisal fabric and sisal rope. These are all materials that cats can really dig their nails into..giving them a great stretch and removing old sheaths from their nails. Corrugated cardboard is another material cats like to scratch.
Types of scratchers vary greatly. There are cat trees that are built with real wood (two by fours, etc., or tree wood). If you can find old, sturdy limbs that won't roll around, bring them in for kitty to try. Get creative and make your own. Just make sure it remains sturdy and won't collapse, fall or roll. Pioneer Pet has an excellent cat scratcher...it's The Ultimate Cat Scratcher (products page). It is solidly constructed and is covered in sisal fabric; a very sturdy material into which cats can really sink their claws. They also have a sisal fabric wrapped scratcher that can be hung or placed on the floor for horizontal scratching. The Refined Feline has a beautiful cat tower (product page) that is a beautiful piece of furniture and has replaceable pads of sisal fabric for kitty to scratch.
Most cats will gladly use their scratcher. To entice kitty to use a scratcher that seems to be ignored, rub it down with catnip, place kitty's favorite toys around it or place kitty's favorite treats around it. Also, praise kitty and offer treats when using the scratcher to reinforce the behavior.