100% do your own thing. Act the way you would act if you were home alone.
For mine I sat on the floor with a pillow and stimmed, because I don't like chairs. I barely even looked at her, because I never do eye contact. I certainly wasn't going to fake it for the sake of pleasantries. A lot of it was done on computer and there are some pen and paper tasks. Just be yourself. Try not to upgrade or downgrade your skills.
Take stim toys, water, snacks, or whatever you think you'll need.
I even took my good luck monster.
Good luck!
_________________
I never give you my number, I only give you my situation.
Beatles