Never encourage bitingand aggressive play by batting at kittens or your cat with your hands.
Cats like a place to scratch and sharpen their claws. To create a scratching post, attach (tack) a piece of old carpeting to any sturdy object. When he/she uses it praise by saying 'Good!' If your pet cat scratched the couch, use gentle discipline and direct him/her to the spot.
Check an adult cat's nails to see if they need clipping. Only the transparent part of the nail should be cut, not the pink area towards the back, or this will cause pain and bleeding.
Dry cat food helps keep the teeth clean and the gums healthy.
Cats can be perfectly happy living indoors all their lives. All they need is a place to climb and play and are happy to have companion pets and lots of attention from their guardians. The big advantage of keeping your cat indoors is safety.
For privacy, provide your friend with a small cardboard box lined with a small soft carpet, so that he can retreat into it whenever he wants to.
Do consider spaying or neutering your cat. It is not a complicated procedure and the benefits are worth it. No unwanted kittens, no males yowling outside your house for an extended period of time. Males do not want to roam or fight if they are neutered and mostly, they will not require to 'mark' their territory all over the place as they are not competitive now.