Photo Checklists. They are a 100% necessity at a wedding. My checklists are a list I write out that has all of the different group variations that we want to make sure not to miss. This could be as simple as the bride and groom with his extended family to the bride's three generation shot (bride, mom, grandma). If there isn't a list, there is a chance of missing the shot. It is that simple.
Also the list will have a list of special poses that the bride and groom want to try to do. We don't use the list for all of the bride and groom formals, but more for those few 'have to get' shots. Most of my shots of the bride and groom are impromptu. I have the bride and groom fill out my checklist paperwork, and from there I write up a list in order of what we will do them on the wedding day. Organization is great!