Advanced: If you have already accomplished this, save more water by 1) installing low-flush toilets, and/or 2) installing a rainbarrel.
Tips for choosing and installing a low-flow shower head:
• To judge your present showerhead's flow rate, hold a gallon container under the head and clock the time it takes to fill it. If it fills up in 15 seconds, the flow rate is about 4 gallons per minute (gpm). If it's full in 10 seconds, the flow rate is closer to 6 gpm. With a low-flow head, it should take 24 seconds or more. (http://www.hometips.com/buying-guides/showerheads-low-flow.html)
• For a review of products, visit this site: http://www.treehugger.com/files/2007/04/earth-day-save-water-shower.php
Faucets
(http://www.energysavers.gov/your_home/water_heating/index.cfm/mytopic=13050
• The aerator—the screw-on tip of the faucet—ultimately determines the maximum flow rate of a faucet. Typically, new kitchen faucets come equipped with aerators that restrict flow rates to 2.2 gpm, while new bathroom faucets have ones that restrict flow rates from 1.5 to 0.5 gpm.
• Aerators are inexpensive to replace and they can be one of the most cost-effective water conservation measures. For maximum water efficiency, purchase aerators that have flow rates of no more than 1.0 gpm. Some aerators even come with shut-off valves that allow you to stop the flow of water without affecting the temperature. When replacing an aerator, bring the one you're replacing to the store with you to ensure a proper fit.
What else you can do:
• Limit shower time to 5 minutes.
• Minimize the time you let the water run; find ways to use water that runs while you’re waiting for it to get hot or cold.
• See http://www.eartheasy.com/live_water_saving.htm for more water-saving ideas.
What you should know:
• There is a worsening trend in water supply nationwide: In 1990, 30 states in the US reported 'water-stress' conditions. In 2000, the number of states reporting water-stress rose to 40. In 2009, the number rose to 45. (http://www.eartheasy.com/live_water_saving.htm)
• Saving water also saves electricity. It takes energy to pump water from its source to a water treatment plant, it takes energy to make it potable, and it takes energy to get it to your house.