When Joseph J. Plumeri took over the reins at insurance brokerage Willis Group Holdings, his first move was to have all the doors taken off the hinges. "My office doesn't have a door. Nobody has a door," he says. "It's a question of making people feel they're making a contribution, and they're part of the process." By moving beyond the old command-and-control culture, Plumeri says he's been able to motivate his workers and tap into their talent and passion.