Don't Be Yourself... Yet
The key word for your first day at work is restraint. If you're a naturally bubbly hyper-energetic type, tone it down a notch [source: Grobart]. You don't want to scare people. Likewise, if your default gear is low and slow, have an extra cup of coffee and practice your best fake smile.
Ease into your sense of humor as well. Even if everyone else is cracking jokes before the meeting starts, don't join the fray just yet. You're the new guy, which means you don't know which lines not to cross, particularly when your boss is involved [source: Sahadi].
And whatever you do, never act like an assignment or task is beneath you [source: Weiss]. If they have you making copies all day or updating the Outlook calendar, don't whine. Once you pay your dues, people will see your potential and let you tackle the more interesting stuff.