What do petit jurors need to know when they arrive on the designated date?

This is my first time being summoned as a petit juror. Is there any information that I would need to know when I arrive there? For example, what do petit jurors specifically do in court? I am summoned to Upper Marlboro in a couple of days and I would like to be prepared. If anyone has an experience they would like to share, it would help greatly. It's sorta getting me nervous because of what "I don't know". Thank you!