Put plants with similar water needs together.

Placing plants with similar water needs together means that you can look after the tender ones a bit more closely while letting the tough ones cope in their drier areas.
This is a simple measure to take for reducing water use in gardens but it is not often repeated to the public gardener. In my work I find that if people have reticulation in their gardens then everything gets the same amount whether it needs it or not. They just water because its easy. When I suggest they turn off a section I get a look of surprise, "Oh, but thats too hard!"
With a little planning and consideration of plant water needs you can pretty much ignore sections of the garden. Tough, drought tolerant plants actually prefer not to be watered too often. They will go soft and can rot if given too much.
For instance, keep all the succulents and cactus in the sunniest areas, so they can be watered once a week or fortnight, or even less. In another area place all your vegetable and herbs; these need much more water so they should also be near the tap if possible so you see them and remember to look after them better.
Many plants once established over one summer will survive on little or no summer watering, especially if the plants are shading the ground beneath them. Allowing leaf litter to build up is great as leaves will break down and feed the soil.
Grouping pots is another time where similar watern needs is important. Some things need a lot, so keep the pots sheltered from strong sunlight to keep the soil and roots cool. Sturdy desert plants, such as agaves and yuccas, seem to make good lone pot plants that can be neglected.

Reuse sink water.
Plants that are nearest the kitchen can be given water from rinsing or from cold water collected while waiting for the hot washing water.