1. Always run your dishwasher with a full load. Most of the energy used by a dishwasher is spent heating water, and since you can't decrease the amount of water used per cycle, filling your machine is more effective than running half-loads.
2. Use the air-dry option instead of the heat-dry, rinse-hold and pre-rinse features. If your dishwasher doesn't have this option, prop the door open after the final rinse cycle to dry your dishes.