Place 2 to 3 inches of mulch around the base of shrubs and plants to reduce water evaporation. Water your lawn only when necessary. If you must water, do it in the morning. Midday watering evaporates quickly, and overnight watering doesn't evaporate quickly enough, encouraging disease. If your lawn is really dry, water half an inch, wait two hours, and water deeply.
Soil can be like a sponge - water can roll right off if it's too hard and dry.
Choose a low-pressure sprinkler that moves in a circle. Oscillating sprinklers can lose up to 50 percent of water to evaporation on hot days. Water your lawn thoroughly and less often.