Do: Communicate
Whether it's your best friend or your sister who's in charge of planning the festivities, talk to your girls about what you envision for the party. Do you feel like going out, or getting pampered -- or both? This is also your opportunity to lay down a few ground rules. Don't be afraid to set boundaries! Totally against any fake penises making an appearance? You're allowed to say so, and even to ban them -- nicely, of course. On the other hand, if you're not offended by a little phallic paraphernalia, let them know that too.