After the first 48 hours there is a real autopilot that kicks in. You need to be sufficiently sleep deprived for it to begin, but that usually takes care of itself.
Remember to enjoy the moments rather than document it all. Its like weddings: they only really need a couple shots. :)
No glass of wine, around the table, big cake shots? Knowing me, I will probably forget to press the record button.
In that 20 minute post-ceremony window where you need to nail about 60 shots, the mom and the dog by the yellow chair is the one I always seem to forget.