Even if you've tried on three different outfits and arrived at the office absurdly early, don't let on that you're nervous. "I tell my clients to smile, regardless of how they're feeling," says Daniel Welch, president of CV Enterprises, a Brooklyn-based recruiting firm. Coming across as a confident team player is vital. "Introduce yourself to colleagues, and tell them you're excited to work with them," Welch says. "And memorize names quickly." That makes it easier to ask questions, another key. "Reaching out to coworkers reassures them that you value their experience," says Debbie Mayer, head of recruiting for a technology company in New York City. Bring proof of citizenship for your I-9 form and a makeup kit for the company badge photo. Your clothes should err on the side of understated. "One woman wore a miniskirt and clunky shoes her first day," Mayer recalls. She was known as the clunky-shoe girl for years. "First impressions," Welch agrees, "can make or break you."