Say hi to the people around you on your first day at work. Since you are not used to those people, you might be tempted to reach in the office and just hide in your desk. A bad impression of you will be created if you do that. Try to great everyone inside the office and the colleagues you meet throughout the day. Also, try to fit into the culture of the office. Do the things they do as long as they are doing the right things. For example, do not go to eat by the cafeteria if you find that everyone eats at their desk.