This article is from the Getting A Cat FAQ, posted to rec.pets.cats newsgroup. Maintained by Cindy Tittle Moore with numerous contributions by others.
You should have your new cat examined by your vet to check for signs of disease or parasites. Ideally, and especially if you have other animals at home, you should arrange to have the new cat examined before you bring it home.
The vet should check the cat's temperature; look for fleas, flea eggs, ear mites, and signs of ringworm; check for overall health and liveliness; and update the cat's vaccinations if necessary. It's also a good idea to have the vet test the cat for common illnesses.
If your new cat is not already neutered or spayed, talk to your vet about when would be a good time to schedule the neuter/spay surgery. Don't assume that your cat or kitten is too young for the surgery; new research shows that neutering and spaying as young as 7 weeks has no adverse affects on the cat's physical and social development.