Only just spotted this. Hope the day's going well for you so far!
Probably too late for you, but for I'll type it anyway for people like Sneeks.
The taking the photos part of it, is the easiest part, the more difficult parts are making sure you're where you need to be so that you don't miss the good shots, and getting the guests to do what you want without being "that bloody annoying photographer" that everyone hates. At this time of year, you've obviously not got that much daylight to use, so make sure you get as many of the must-have shots as early as possible. Also, take a couple of off-camera speedlights with you, they'll give you something to use not only when it gets dark outside, but also for the speeches, first dance, etc... I know you'll be doing mainly reportage-style shots, but most couples will expect at least SOME posed shots, such as with bridesmaids/parents/bestman (or bestmen)/etc. Whenever you do group shots, start off with the biggest group, then let people go as they're done, as nobody likes standing around when there's a bar waiting! Also, try not to just have everyone stood in a straight line, most people got bored with that look back in the '70s, so get creative.
Probably the most important thing to remember though, is to have fun. If you look like you're enjoying yourself, people are far more likely to feel the same way around you, which makes it easier to get them smiling in the photos!
Good luck, and feel free to show us a few of your results!
