Before you leave the house in the morning, make sure that you have all of the equipment that you need for the day. Make sure your batteries are charged. Be certain that you have plenty of batteries (for camera and flash unit). Make a list the night before if you need to and check things off as you’re loading it into your car. Make sure that you have a full tank of gas. Sometimes the couple will want to go places between the ceremony and the reception, such as the bar where they met or to visit an elderly person who wasn’t able to make it.
Also, take a few bottles of water. It’s going to be a long, fast-paced day, and you need to stay hydrated.