"Consider not flushing without a "solid reason." If your bathroom gets some ventilation, simply close the toilet lid and wait to flush until you really need to."
That's advice from Jerry Peek's Off-the-Wall (but really simple) Water-Saving Ideas. This guy doesn't waste a drop of water. If he turns on the faucet, he either uses the water or catches it in pitchers so he can use it later. You know what I'm talking about. You want hot water. You run the tap and wait until the water feels warm. In the meantime, lots of cold water runs down the drain. Following Jerry's suggestion, you would catch that water and then use it to soak dirty dishes.
His site has energy-saving ideas too. He uses only the pilot light for his well-insulated hot water heater. He claims it gets the water warm enough for normal uses. Once in awhile he'll turn on the main burner. I wonder what his showers are like?