I've had my first day in a company about 15 times. The most entertaining is when I and a new chap were starting on the same day and we got mixed up. It was a bit embarrassing as they were expecting a fluent German speaker, which I was not.
On another time, they did the usual introductory stuff in the morning, but come afternoon, they didn't really have anything for me to do. No problem, I said, I'll take the afternoon off. So I did.
Usually, all I need to know is
1) Where do I sit?
2) What are my ids and initial passwords?
3) Where's the coffee?
4) Where are the WCs?
5) What do you want me to do?
Especially point 3.