Just be honest with your doctor. They will probably ask the usual questions such as any past health issues, how long you have been living as your gender, how long you have felt that way, simple stuff like that. It took me about a month (I think it was about 4 visits) before I was actually given a letter of recommendation to start T. My gender therapist took me out to the store and stuff to get an idea of how I am in a public setting. She wanted to see how my mannerisms were, how people perceived me. It was actually all quite interesting. Obviously each doctor will differ.
When you get your letter of recommendation then it's all easy street from there. My first appointment with him he just asked me the same basic questions, past health, family history. He then took me to an exam room and gave me a physical exam. He felt my lymph nodes, took my blood pressure and weight. He also felt around my boobs which was a bit awkward and felt around my abdomen (he did not touch my privates so don't worry about that lol). Lastly he took my blood, I guess to just get an idea of what I got going on there.
I didn't get my prescription until I went in for my next appointment. He also diagnosed me with hypothyroidism which really explained a lot of symptoms I have been dealing with for a long time. I also have a goiter which is an abnormal enlargement of your thyroid (but it could also be a hereditary thing because my grandma had one). So long story short he gave me a prescription to take care of that as well. He did send me for and ultrasound on my thyroid just to make sure there was no cancerous lumps or anything. All they found were little air bubbles so that was good to hear and see.