I also support William's ideas on setting up the night before if you are going out at dawn. I even go a bit further and use a custom setting on the camera to ensure that the ISO, mirror lock up, f stop etc are all ready to go when I turn on the camera. I think quite a few DSLRs have a custon setup option now. I use a second custom setting for multiple exposure shots, which are often useful after dawn when the shadows are more prominent.