Cats have a natural urge and need to scratch their claws on something from time-to-time. This can have to do with maintaining their claws, marking their territory, stretching, etc. It may also have to do with ways they've learned to interact with you such as getting your attention or expressing emotions and releasing energy.
They tend to go to the same objects over and over again. Unfortunately, if cats are not provided their own scratching items then they're more likely to use furniture, carpet, walls, woodwork, or other items you may not want scratched up.
Trying to get your cat to simply stop scratching altogether goes against natural instinct. If you're considering declawing your cat you'll want to first read up on this controversial procedure. The best solution is simply to offer one or more items that can be used for scratching and redirect your cat away from the items you don't want scratched.
The first thing that probably comes to mind is a scratching post which takes the form of an upright post with rope or other scratching material wrapped around it. However, a scratching post is only one of many forms of cat scratchers. Scratchers can also be flat surfaces that lie on the floor or an inclined surface, be part of another structure such as a cat tree or piece of furniture, or take on a wide variety of other shapes and configurations.
The three basic considerations when choosing a scratching post or scratcher are:
Cats have preferences for what they like to scratch. One of those preferences has to do with orientation of the item and another has to do with the feel or texture of the scratching surface.
Whether standing on it's own or attached to something else, a scratching post is usually oriented vertically or upright. Your cat reaches up on the post and pulls down on the scratch.
Some scratcher pads can also be mounted in this vertical orientation.
Scratchers are also oriented to lay horizontally or flat on the floor with the scratch not so much a pull down but a pull back. An angled orientation is somewhere between the vertical and horizontal orientation.
Your cat may give you clues as to its preferred scratching orientation (e.g., a tendency to reach up and want to scratch the furniture/walls or reach out and scratch the carpet).
Three materials are generally used for a scratching surface with scratching posts and pads.
Sisal rope is the most common material you'll likely see used on scratching posts (other ropes besides sisal may also be used).
Sisal fabric may be used as a cat scratching material as well. The fabric may be wrapped around a post, lay flat on the surface of a scratcher, or even be used by itself as a scratching mat.
Carpet can be used by itself on a post or other scratching surface or in combination with other materials. It's very often used on the base of scratching posts as well.
The third type of material commonly used for a scratching surface is cardboard. There are generally two types of cardboard used with scratchers: 1) corrugated cardboard, similar to what you might find with a cardboard box, can be considered disposable because it doesn't last as long as other materials and 2) high-density cardboard which lasts longer and can come in a wide variety of shapes (e.g., loungers that your cat can lay on).
Whatever the material used with a scratcher, each material will have a different feel or texture and your cat may have a preference more for one than the others.
Both a post and a pad should allow your cat to fully stretch the body. This means it has to be tall or long enough to accommodate your cat's outstretched body.
A vertical scratcher will have to incorporate almost your cat's full length in its height but a horizontal scratcher can often be shorter because your cat is more in a bent at the hips position when scratching horizontally.
Stability of scratcher
Your cat also has to feel safe using the scratcher. If it doesn't have a solid base and wobbles, or worse yet tips over while your cat tries to scratch it, then your cat may avoid it.
Not all cats use a scratching post in the same way. While some cats walk up to the post and gently start walking their paws higher as they scratch and stretch, other cats attack the post by jumping at it or climbing on it.
If your cat attacks and climbs the post then it may be time to look for a cat tower or similar item that can not only be used for scratching but also climbing and perching. You may also want to look for a product that can be attached to the wall or some other sturdy support.
Some scratchers can have a funny smell to them that turns your cat away from it. Often those smells will dissipate over time. You may just have to be patient until it does or you can do things to try to get rid of that smell (e.g., airing it out in some way or spraying it with something more appealing to your cat).
You'll want to place the scratcher in a location where your cat is going to use it. It shouldn't be far from where your cat hangs out.
If your cat has already begun scratching something of yours then you already have a good clue as to where you need to place the scratcher.
If your cat hangs out in more than one place you may simply want to get a scratcher for each location.
There are also some tricks you can try that may draw your cat to the scratcher (like sprinkling some catnip on it, spraying it with something to attract your cat, placing favorite toys by it, etc.).
Sisal rope and fabric is probably the most durable material commonly used. The rope can also be replaced when it wears out as a relatively simple DIY project.
The dense cardboard items may start to look shredded over time but they often have multiple sides where you can just flip the item over to get a new scratching surface.
The cheaper corrugated cardboard pads will have the least durability and you may want to think of them as disposable items. They're often sold in a pack where you just throw the worn one away and pull out a new one.
Carpet is often used as part of some products (i.e., the base of a scratching post, the covering for a cat tree, etc.). How long it lasts will depend on how often it's used as a scratching surface. It should last longer than corrugated cardboard but probably not as long as sisal rope.
When it comes time to replace a scratcher, you may want to simply put the new one next to the old one and allow your cat some time to claim the new one before getting rid of the old one.
Most cat scratchers are obvious as to what they are and eventually show their wear from frequent use.
You can try to hide them in a location where company won't see them but then your cat may not use them if that's not where your cat hangs out, especially if your cat wants to be around you.
You may however, with the right product, be able to hide the scratcher in plain sight.
Modern cat furniture doesn't look like the typical cat product.
Cat lounger scratchers come in a variety of shapes that serve a dual purpose (cat lounge and cat scratcher).
There are also less obtrusive products for cats to hangout in that have scratching surfaces.