Wash only full loads in your dishwasher, using short cycles for all but the dirtiest dishes. This saves water and the energy used to pump and heat it. Air-drying, if you have the time, can also reduce energy use. Also, look for eco-friendly dishwasher detergents free of phosphates and chlorine bleach, like Method's Smarty Dish. They're in capsule form and will make eco-washing easy as pie.