At 100 gallons a day for a typical family of four, the toilet is probably the largest single factor for daily water use. So, finding a way to reduce the water usage of your toilet can have an immediate effect on water use.
Aside from the obvious cost benefit, it's also kind to the earth.
Most toilets will allow you to adjust the water level down a bit, saving you some money. But, if you can't find the adjustment, try the following trick:
Find a water bottle that will fit inside your toilet tank without interfering, and fill it with water and a few rocks so it won't float. Use one large bottle, or several smaller ones. Two quart-size bottles will reduce your toilet's water consumption by about 10 percent. Also see our leaking water calculator to see how much water a leaking faucet wastes.