Put a plastic bottle in the toilet tank. Put an inch of sand in a quart bottle to weigh it down. Fill the rest with water and put it in your tank, away from the operating mechanism. In the average home, this may save five or more gallons each day. Take shorter showers.
Older showerheads use five to ten gallons a minute.
Install water-saving showerheads. A quality water-saver showerhead provides a luxurious shower, yet uses no more than 2.5 gallons per minute. Ask your hardware retailer for advice. Take baths instead of showers. A partially filled tub uses less water than all but the shortest shower.