Avoid washing dishes under a stream of water. Turn off the water in between dishes. Use only a full dishwasher and clothes washer.
If you like a drink of cold water, but you have to let the tap run for a while before the water gets cold, instead keep a pitcher of water in the fridge.
Save the water from steaming or boiling vegetables for houseplants, vegetable broth for soup or stir fry liquid.
Wash food in a bowl or pot of water rather than in running water. This works especially well for herbs because you can swish them around and the dirt will come off their many surfaces. Let the herbs sit a minute and the dirt will sink to the bottom while the herbs float at the top.
Do not use water to thaw meat. Use the microwave instead.
Avoid using your garbage disposal system in your sink. It uses lots of water to run. Compost your scraps instead.