Plant shrubs and trees that nature designed to look green and full here on Maui without a lot of water. Make sure they get regular watering in the first year or two, to help them establish good, deep roots. Then, once they are grown in, you can cut back or stop watering, depending upon your location. At worst, in our hot, low southern areas an occasional, slow, and deep watering placed right at the roots should be enough to keep a climate adapted plant looking good even through the hot summer. Check and repair all of your outdoor fixtures regularly.
Drip irrigation is designed to get water slowly and directly to the roots of plants.
This not only saves water, but for some plants it helps to reduce the risk of diseases. Sprinklers with fine, high sprays lose a lot of water to evaporation. So, if you do use a sprinkler for certain plants, go for the sort with low, flat spray patterns and larger drops of water. Check timers on irrigation controllers and adjust them monthly to water appropriately for the season. But if you use a hose, set a kitchen timer or buy a timer attachment that hooks on between the faucet and hose.