• One inch of water a week (rain plus supplemental watering) should be plenty. After heavy rain, you may not need to water for 10-14 days.
• Water very early in the morning.
• Never water when it's windy, rainy or very hot.
• Raise the blade level of your mower to 2 -3 inches or more. Longer grass retains more moisture.
• Never water faster than the soil can absorb it. Avoid puddling and run-off.
• Be sure your hose has a shut-off nozzle. Hoses without a nozzle can spout 10 gallons or more per minute.
• Do not apply fertilizer in the summer - new growth requires more water. Apply in early spring and or fall.
• If you have an automatic sprinkler system, make sure the timer or "controller" is set to water each landscape zone efficiently. Program the controller to operate according to the watering needs of your lawn or garden. Better still, install a rain sensor or soil moisture sensor that turns the system off if it’s raining or if moisture is present in the soil.
Source: http://www.ranchowater.com/index.aspx?nid=196