You can check references exhaustively, go over your expectations repeatedly, and establish the most thorough set of rules, but there's no guarantee you won't eventually need to fire the person you hire. "It's a crapshoot, really," says Letitia Baldrige, author of Letitia Baldrige's Complete Guide to the New Manners, $30, www.amazon.com. "They may not chemically react well to you, or you to them. You'll be lucky some of the time; you'll be unlucky some of the time."