I went the other way, had cats all my life and got a dog later.

If the cat is from the shelter (and I SO encourage you to!) they are going to be grateful to be out of the shelter environment to begin with, and because your home will be completely new, s/he should adjust to a dog. That being said, I would slowly introduce the cat to the dog, maybe keep them separated in a room but can smell each other for at least a couple of days.

I think all our cats had some sort of scratching issue, but those are usually remedied by what others have said: scratching posts, or putting double-sided tape on sides of the furniture.

And there always seems to be at least one poor kitty at the shelter who'd been declawed. Declawed kitties need homes, too.

If there's going to be outdoor access, I've found that for the most part females don't tend to wander as far and wide as males do.

And (sorry this is getting so long!) most shelters these days do some sort of personality assessment of the cats. Just look for a cat that's boldly lounging in the middle of all the action - if they're mellow in a shelter setting, they can only be mellow at home!