Though I'll be onsite to answer all of your photography-related questions, I wanted to offer a bit of advice to the brides who can't make it: Scout out other wedding albums for posing ideas, and create a detailed shot list of the "must-have" moments you want your photographer to capture.
Of course, there is also something to be said about allowing your photographer to snap pics, spontaneously, as the magic unfolds. Extraordinary moments of joy, laughter, intimacy -- that's what makes this day so memorable. As a photographer, that's what I try to preserve.
Above all, communication with your photographer is key. It's sort of like a marriage, but just for one day.