Your first day is here. That time off sure flew by, didn't it? Put on the one suit that you know makes you shine. If you feel confident, you'll look confident to others. Whether you're driving to work or using mass transit, be sure to leave plenty of time to get there early. Treat it like a job interview, and remember first impressions do count. Eat breakfast before you leave your house -- fresh breath and clean teeth (no poppy seed bagels, please) are a must.
Your work day begins when you leave your house. You never know when you'll come into contact with your co-workers or boss. A friend of mine was driving to work one day when a car swung around her and the driver made a hand gesture (you know the one) at my friend. He didn't see my friend's face, but she saw his. It looked familiar and then my friend remembered why. He was her most recent hire, starting work that very day. She attributed his action to nerves, and hasn't said a word to him. Yet. You shouldn't make lewd hand gestures regardless of who the recipient may be, but if you are tempted to, just think of the other person as being a potential boss, co-worker, or client.
So you finally made it to your new workplace. Now take a deep breath and walk in with a smile on your face. Keep your head up and remember to make eye contact. Be polite and friendly to everyone you encounter, whether it's the receptionist or the mailroom clerk, your colleagues or your new boss. Introduce yourself to those you meet and remember that it's okay to ask questions. People generally like to help others and it usually makes them feel good about themselves. I remember a new co-worker who refused all offers of help. I guess she thought it would make her look incompetent to our boss. The result was that everyone thought she was a snob or a know-it-all and some people even vowed to refuse to help her in the future.
While it's okay to hold onto some of things you learned in your previous jobs and use that knowledge in your new job, remember that every workplace has it's own way of doing things. Your first few weeks or even months on a job is not the time to change the way things get done. Do not utter these words: "That's not how we did it at my old company." Your colleagues will just be thinking this: "Well, you're not at your old company and if you liked it so much why didn't you stay there."