According to an article from Reader’s Digest, let your dishwasher (if you’re lucky enough to have one) wash the dishes and stop doing them by hand.

If the dishwasher is always only run when it’s full, it will be about 1/3 less water than doing dishes by hand (all the rinsing uses a lot of water).

If you already have a dishwasher but it was manufactured before 1994, a new Energy Star rated dishwasher

Now you have an environmentally sound reason for getting a dishwasher. Just make sure to look for an EnergyStar rated one.