Where does your cat want to scratch?
You should have as many cat scratching posts in your home as you can afford, both in terms of money and interior attractiveness. Besides, not all scratching posts are equally good. You can learn what makes a good scratching post here.
You will likely need at least one scratching post in each room, and several in the rooms where your cat is most active. If you do so, choosing the best location for them becomes less important because, according to probability theory, at least a few of them will be in the right places.
Photo by Arria Belli.