"People working in the same building often dress in sync," says Kat Griffin, who founded Corporette.com, a site for professional women. She realized this simple truth after showing up at her conservative Wall Street office wearing what many magazines told her was appropriate (revealing wrap dresses and fishnet stockings) or frumpy suits, neither of which did her any favors. Have a cup of coffee in the morning near your potential new office or drive by during lunchtime and watch people going in and out. Just don't do your investigating on a Friday when many companies' dress codes are more relaxed, says Brenda Arnold, regional vice president of Robert Half International, a staffing firm. If you're still unsure, make a call to a local professional organization (like the local bar association if you're a lawyer) to see what they recommend.