I had two cats when we got our first dog, Max (who was an adult at the time). One cat had experience with dogs, the other did not, and we didn't know whether Max had ever been around cats. We set up a room with a baby gate so that the cats had a "dog-free" space they could go to. After a few months, we took down the gate and they've been living together ever since. The cats and Max are not best friends, but they all tolerate each other, and Max knows to back off when the cats tell him to. They have been living together for 11 years, and one of my cats STILL hisses at Max when he gets "too close" according to the cat. (This cat also searches for Max if he's gone to the vet or is boarded, so hissing is her way of showing affection to him!) When we got Star (adult Great Dane), the cats hated us for a while, but they got over that too!
Here are my suggestions: If your cat typically free-feeds, you'll want to put thae food in a place the puppy can't get to (most dogs love cat food). I've typically fed my cats on a table (until recently when my oldest cat couldn't jump up on the table). You may also want to put the litter box where the puppy can't get to it as well (some dogs eat kitty poop!). Making these changes before the two are living together might be easier on the cat.
Good luck!
Tracy