Dr. Charles has a nice writeup of his experience with a transsexual patient, and I really respect him for trying to be sensitive and respectful. (When’s Stanford gonna start showing gay pr0n?) He did the right thing; above all, listen to your patient. And it’s okay to be ignorant (I don’t think doctors do it enough). The point is to have the willingness and interest to learn.
Just two notes: some people prefer transgender to transsexual, it just depends on the person. And a drag queen is not the same thing as a transgender person.