Install water-saving devices on your faucets and toilets. A low-flow showerhead could be a good start.
Don't wash dishes with the water running continuously. Use a method that requires less water to get the dishes clean.
Turn off washing machine's water supply to prevent leaks. It doesn't need to be on all the time.
Replace old toilets with new ones that use a lot less water.
Wash and dry only full loads of laundry and dishes. Doing a half-load wastes water.
Don't use too much water to water your lawn.
Don't leave the faucet running while you brush your teeth.