1. Install flow-rate reducers at each of your water points (kitchen sink, shower, bath-tub, etc.) It may reduce the amount of water usage by a third!
2. Install a pressure reducer for the entire house.
3. Repair leaking toilets (listen for that constant hissing sound and constant water seepage into the toilet bowl). Tens of gallons of water a day can be lost.
4. Install a gray-water system that recycles your gray water for garden maintenance purposes or for filling your toilet tanks.
5. Make sure that all your toilet tanks have a half flush and full flush option.
6. Make sure that your toilet tank is not over filling. You can lower the level of water in the tank and still have an effective flush.
7. Consider reducing the water level in your tank even more with a device sold by ecobuyit.co.il.
8. Install a water-less toilet.
9. Fix your leaky sink (you can see how much water you lose by even a drop every second or two by putting a bucket underneath the leak).
10. Run only full loads of laundry and full dishwashers.
11. Turn the water off in the shower when lathering. Turn water off in the sink when not rinsing off the dishes. And you can rinse the dishes just fine without having the water on full blast.
12. Re-use water from your air-conditioner to water flower plants, etc.