An all dayer is tough no matter what you do,it reminds me of pulling guard duty in the millitary. The obvious are these,get plenty of rest the night before,don't get out any earlier than you have to. Stay away from to much sugar,eat light in the morning but eat well. I like wheat toast with peanut butter and honey, I substitute cliff bars for my snickers or paydays for all day hunts and gatoraide for my water and I get some green apple gum to chew on.I try to rest my eyes while I feel fresh which seems to help me later when I'm tired. A relaxed focus is less tiring than a intense stare as well. Lastly If I dress to warmly it makes taking a nap easier so I try to find a ballance between being to warm and getting chilled. If I get chilled I stand and stretch as quitely and slowly as I can.