Plant appropriately. Plant small trees under big trees. This will help prevent evaporation and provides some shade for your plants. You can also plant a shade garden under trees.
Native species will be adapted to local water supplies, and therefore need less supplemental water.
Consult with your local nursery on designs.
Know how much water plants need to thrive, and don't apply more water than that.
Grow plants with like water needs together. Sometimes called "hydro-zoning," this method simply means that plants are grouped together by water use, so that they can all be watered appropriately.
Use furrows and basins. Dig low areas to water only the root zones of your plants, not bare areas around them.
Use sub-irrigated raised bed gardens (for example wicking beds, global buckets, Olla irrigation, and Earthbox planters