Do as much cleaning as possible with cold water to save the energy used to heat water.
Check your faucets for leaks. They waste both water and energy!
Conserve hot water by installing water-saving showerheads.
Once your water is hot, insulate to help keep it that way. Wrapping exposed hot water pipes with insulation will minimize heat loss. So will installing an insulation blanket around your water heater.
Reduce your water heater's temperature to 120 degrees Fahrenheit. That will produce plenty of hot water and still save energy. For homes with a dishwasher, a setting of 140 degrees is required to clean properly, but most of the new dishwashers have a built-in water temperature booster.
Replace old hot water heaters with more efficient technologies like heat pump or on demand hot water heaters.
Many new water heaters have a "vacation" setting you can use to save energy if you're away for more than a few days. Turn the thermostat "down" or "off" when you're gone for more than three days.
If you have a pool or hot tub, make sure you keep it covered with a well-insulated cover when not in use to keep heat inside.