Ok these things always start with the basics - name, age, date of birth, etc. They might take your weight and height (sometimes they do, sometimes they don't).

They'll ask you about your symptoms, and what concerns you in your life.
They're probably going to go through your medical history, both physical and mental.

They might ask you about past interaction with psychiatry. Maybe they'll ask you what you've been diagnosed with, what drugs you've taken.
You don't have to know everything that's ever happened; but obviously the more you know, the better. They're not going to punish you if you don't know your whole medical history.

They might take some blood tests, measure your BP.

And remember: if there is anything that makes you uncomfortable, you have a right to refuse it.