Dishwashers use less water than washing the equivalent amount of dishes by hand.
Do not pre-rinse dishes. It won't kill you to have dirty dishes in your dishwasher.
Wash only full loads.
I have to run my water first to get it hot, because the sink is so far from the water heater. If I were a better person, I'd be capturing that water for other uses, such as watering plants and flushing.