Drought is upon us in earnest--substantial water conservation is necessary. We all have to do our utmost, around the home, and in the yard and garden to conserve water and use it wisely.
There are probably four things that are top-tier in saving water in the garden:
- Removing as much lawn as possible
- Irrigating smartly--mostly with drip irrigation
- Mulching properly
- Water-wise plant selection, such as natives and Mediterranean-climate plants
And for this summer, delaying the planting of ANY new plants until fall, just before rains, is the best idea.
Removing and Replacing Lawn
Lawn takes far more water than anything else. Gardeners and homeowners should seriously consider lawn-replacement: replacing all - or at least part - of thirsty lawns with low-water use plants. There are several different techniques for taking out lawn, and many alternatives to supplant it.
Irrigating smartly 
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Using minimal water to keep plants alive and healthy in the dry season, and wasting nothing are the watchwords. If you have sprinklers, make sure there is no overspray outside the area which needs water. Watering the right length of time, and at the right times are, important, too. Drip systems are the best way to minimize water use in irrigation--drip is over 90% efficient, whereas hand watering and sprinkers range only from 50-70%. Irrigate slowly and deeply, to encourages plants to develop deep root systems that are better able to tolerate drought. Periodically check soil moisture with a moisture meter or a soil sampling tube, which extracts a 12-inch or longer core, showing inch-by-inch how wet or dry the soil actually is.
Also, group plants according to water needs--a practice known as hydrozoning. It's critical with drip irrigation, and a water-conserving practice even if you water by hand.
Water-wise Garden Design and Plant Selection
rhamnus_californica
Remember that many landscape plants establish themselves faster when planted in native soils with little or no amendments. This is especially true for California natives. Plant in the fall whenever possible to allow young plants to establish themselves with the help of winter rains.
Mediterranean, Xeriscapic and Native plants make beautiful gardens
Other Water-saving strategies
Re-cycling and re-using household gray water is an idea whose time has come. This can range from simply diverting bath and wash water to a tank for later re-use in irrigation, to a more complex system combining a sand filter, holding tank, pumping system. A few package systems are commercially available.