If you want to stop your cat clawing the furniture then there are 3 things you need to know. Firstly why does your cat claw your furniture? Secondly how do you tell your cat you don't like their behaviour? Thirdly what do you give your cat to claw as an alternative? and how do you train your cat to use the alternative? (You probably noticed that's four things but really three and four are so connected it's almost the same thing!)
OK, so why does your cat claw your furniture?
Cats need to keep their claws in good condition. They need sharp claws for climbing, catching food and protecting themselves. So clawing your furniture helps your cat sharpen their claws so they can climb the fence, catch you a mouse and protect themselves from the other cats in the neighbourhood (also your cat really enjoys the clawing sensation.) You don't want to stop your cat from being a cat do you? So you need to know that cats need to claw and you need to find your cat an alternative to your furniture to claw on.
Pretty simple so far now this is the bit where you come in.
When you catch your cat clawing your furniture say NO!! Use your cats name too at this point. My cat is called Timmy so when I catch Timmy doing stuff I don't want her too I say NO TIMMY firmly. You don't need to shout just speak firmly remember you want your cat to stop clawing not to be scared of you.
(You're probably thinking Timmy is a not a girls name – not my fault she's a rescue cat so that was the name she came with and she likes it)
Moving on to stage three – the alternative to your furniture is a scratching post or in Timmy's case a scratching mat (she likes to be a bit different to other cats.) Some cats prefer to claw horizontally (mat) some cats prefer to claw vertically (post). So make or buy a more attractive place to claw/scratch than your furniture. There are lots of posts available from pet stores or on-line and a great variety of prices so you should have no problem finding one that fits with your budget. (Timmy has a front door mat which she loves)
Last step is to put your post/mat close where your cat is clawing the furniture. When you've said NO TIMMY (don't forget to use your cat's name not mine). Pick up your cat and put them on the post or mat, do pretend scratching with them and praise them. Big thing is to praise for the behaviour you want to encourage and just say NO to behaviour you don't like. Continue with praise for the scratching post and NO whenever you catch your cat clawing. For an additional incentive rub some Catnip or Catnip oil on the post/mat. (You're thinking that's 5 things aren't you? Actually I see it as three things, a bit more information and a tip!)
Cats are very smart and usually learn to use the cat scratching post within a few days.