Always DRESS THE PART. You are working in a law office and should dress appropriately. That means you wear a business suit. Men: slacks, jacket, button down shirt, tie, dark socks, and nice polished shoes. Women: dress pants/blouse/jacket, skirt/blouse/jacket, dress/jacket (pantyhose included), neutral tone shoes. Make sure your accessories are simple, you’re well-groomed and clean (always shower, brush your teeth, wear deodorant, etc...) How you dress the first day will set the standard for yourself and for people you come into contact with in the office and in the community.
Arrive early or right on time (never late).
Pay attention throughout your first day. Ask plenty of questions - this is the time to ask.
Smile and be friendly, but try not to make your first day entirely about the people you meet and attempt to make it more about the work you are to complete.
Shake hands with everyone you meet. If someone shows you how to do something or helps you out around the office in any way, remember your manners and say "thank you." Those moments of gratitude will go a long way.