Perhaps you want to introduce an old friend to your new work friends, or you know a new mom who'd like to join your usual group of moms. Be sure everyone knows what to expect - if you're going out with a group of childless women, then it's probably not OK to bring your own child along. Discuss the kid factor well in advance so that no one is unpleasantly surprised. Don't let the festive mood become depressing with an all-out bitch session. It's one thing to hash out a few guy problems - it's only natural for women to talk about their partners - but allowing the night to devolve into a man-bashing, tearful event is a major downer. Finally, a little common courtesy goes a long way. Focus on your friends, not flirting and hooking up, unless you've all discussed that as an objective before the night began. Also be sure to put your phone on vibrate to avoid distractions.