Turn the brightness down as low as you can handle. The screen is the biggest battery killer.
Anything that moves is #2. Minimize hard drive and optical drive use. Watching a DVD will kill your battery really fast since it needs to constantly spin the optical drive.
I would suggest opening up all the applications you will need while plugged in. Starting up apps hits the hard drive. iTunes also uses up a lot of battery since it makes the hard drive spin for each song.
Close the lid before you go through security. They will probably make you confirm that it is a working computer. You don’t want to waste battery proving that your computer is not a bomb. Just close the lid again. Every restart sucks up a lot of power.
And turn off WiFi and Bluetooth.