I recommend the cheap cardboard scratches which come with catnip, all my cats like those and buying a study vertical post covered in carpet of sisal rope.

Or if you have the money and space you can go for a large cat tree which allows the cat a choice of vertical and horizontal surfaces in carpet and rope.

The important things to note is that a post has to be sturdy and not move when the cats uses it, for this reason I would not recommend the scratching pads which you attach to door handles.

Though the cheap cardboard scratchers are fine as the cat sits on them and the cats weight anchors the scratcher.

I don't use water sprayer with my cats, I don't feel it works.

We place posts near cat sleeping place, as our cats wake up and stretch and scratch as a wake up routine.
Like Debbie says, if the cat scratches elsewhere we pick them up and take them to the nearest post and gentle run their paws down the post.

If the cat gets the idea and scratches the post by digging in, we praise the cat with load of cuddles. Sometimes I'll scratch the post myself with my finger nails to show the cat what to do.

There are loads of ways of stopping a cat scratching a sofa etc but the most efficient method we have found is to cover the sofa in a soft blanket and place a post close by.