If your therapist has an intake form, be sure to fill it out before you go if you can. (I am allergic to intake forms, because they give you one line to answer questions that would take me a week). If they have a form, they will probably spend the first session getting to know you and going over what is on the form; if not, then they will be asking you similar questions: what name would you like me to use to address you? do you have favored pronouns? what is your goal (goals) from therapy? do you have suicidal thoughts? are you depressed? are you anxious? have you seen a therapist before? are you on any medications? have you ever been treated for mental illness? do you have other medical conditions I should know about when treating you? what is your marital or relationship status? do you have any problems or issues you would like to work on? have you suffered trauma? child abuse? sexual abuse? car accident? death of a loved one? do you have symptoms of PTSD? Why did you come to see me? How are you doing? How are you feeling right now? ....
that sort of thing! A gender therapist may also specifically ask you if you are on hormones, what gender(s) do you feel apply to you, do you need someone to write you letters, and questions that would bring out dysphoria about your body or your gender.