Gabe Weatherhead:

Reduce the fricking screen brightness! They even put shortcuts on the keyboard to do this. They're trying to give you a hint. Lowering the screen brightness is the single biggest change to cut power consumption. Don't just lower the brightness. Try to go as dim as you can without squinting. I suggest lowering the brightness several days before you leave. Get used to it and then lower it more. You can always increase it with the keyboard shortcut.