Even though a lot of his article refers to dogs and not cats, there is still a lot of wisdom in Scott Weese's post on this subject over at Worms and Germs.
#1 and #9 are probably the most important in our office. Confining ALL cats to secure carriers prior to entering the exam room is critical for the safety of your pet, other people's pets, you, and other people (including the veterinary hospital staff, whose job requirements do not include getting bitten or scratched). Leaving small children at home makes for a more relaxed cat - when frightened and in an unfamiliar environment, cats lose the ability to recognize familiar people and be comforted by them.