Water the yard after sunset and do not mow the grass real short, set the mower for high cut. This will save on evaporation of water and thus less watering.
Limit shower time; have every thing ready to shower so you not running water when you are not showering, you will save electricity as well.
Do not have the washing machine set on large load when only a few things are to be washed.
Check for plumbing leaks, just a drippy faucet can add up to hundreds of gallons a year.
Also if its raining hard it’s a good time to wash the car.
You can install a cistern to catch the water run off from the roof of your home and garage to be used for the yard or washing the car. A filtration system can be installed to use the cistern water for other uses. But if you live in an area of high air pollution I would not use the water for drinking.
Oh and if you run the waste water from your sink, to the tolit tank, as one person suggested, it will make a mess in the tank over time and screw up the ball assembly that makes it flush. Scum and debris can prevent the toilet valve from closing all the way and it will cause the toilet to keep running water through.
http://www.zone10.com/tech/NASA/Fyh.htm