One simple way to save water is with a dual flush toilet. This one, the “Persuade” by Kohler, has a standard flush of 1.6 gallons plus an optional flush of 0.8 gallons — cutting water use in half.
To word this delicately, for most of our flushes, the 0.8 gallon option will be adequate. This will save a large amount of water annually. List price for the white one is about $360. Not too bad.