Don’t overcharge
When your camera battery does need recharging, do so, but don’t leave the battery on the charger all week.
Dim the LCD
LCDs are the biggest component to draw power on your camera battery. If possible, dim the brightness to save battery life.
Use the LCD as briefly as possible
Turning the preview setting off may be the most helpful tip here.
Stop deleting images from the camera
If you’ve got a large memory card (you should), there is no need to delete images on the camera itself. Wait until your back at the computer to so. This can really drain battery life.
Use an external flash
Pretty self explanatory. If you often shoot with the flash, get yourself an external. The results will be much better and as an added bonus, your camera battery will thank you as well.