For my first session I was sooo nervous I didn't really sleep, when I got on the coach to London I put my headphones on & spent the 4 hr journey listening to Mike Oldfield & Enigma so by the time I arrived I was in a very calm state of mind.
My psychiatrist was very friendly & approachable, he asked me lots of questions about my history of being trans such as when I first realised I was trans, why did I feel I had to hide it, school life, family life etc.
The best advice I can give is not to worry & be honest, when I had my second appointment over a year later a different psychologist covered the same ground & had I told porkies then he's have caught me out as I often forget what I said yesterday, never mind what I said a year ago, this is why I say to be honest.
I imagine it would raise red flags all over the place if they thought for a second I wasn't being honest.
Best wishes
Jayne