I'm getting ready to go dress shopping for the first time and would love to know what to expect. Aside from making an appointment, and taking in some photos of dresses I like, what else should I make sure to do? I know people mention to bring the undergarments that you plan to wear, but how will you know what you need without having the dress? I'm assuming they just mean like spanx and a strapless bra? So when you find "the one", and you're ready to order, what's the common down payment you usually pay? 50%?