Always run a full load. Just like other major appliance, it will use same amount of energy on matter the load size. If possible use AIR-DRY. AIR-DRY saves more energy. Use Jet-Dry, it will allow your dishes to dry quicker. Always run your sink water unit it is Hot. Filling your Unit with Hot water will improve your end result.
A great way to clean your Dishwasher. Take White Vinegar, a Tall glass or coffee mug, fill it to the top with Vinegar, place glass up right on the top rack in the center. No Soap or dishes.
Turn on your longest and hottest cycle possible. Do this once a week or once a month.