Load your automatic dishwasher to capacity before running it. Place a layer of mulch around trees and plants so more water can be retained by the roots. Wash the car with soap, water, and a bucket, using a hose with a shut-off nozzle for a quick final rinse. Adjust sprinklers so only the lawn is watered and not the house, sidewalk or street. Cover pools and spas to cut down on evaporation.
Longer grass means less evaporation.
Let grass grow taller in hot dry weather by setting the mower one notch higher. Aerate your lawn.