If it doesn't say so in the packet, call and ask if you should be fasting when you come in. It'll depend what kind of blood tests they want to do, and if they do them on site on the same day. Mine did, and they forgot to tell me to fast. Luckily I had a friend who goes there who warned me.
If they're trans-friendly and have prescribed to folks before, expect to go over your medical history, mental health history, and lifestyle. It is also a good idea to look over your insurance and see what forms of T they will cover, if you are considering topical gels/creams.
Good luck!