Whether you are creating a new garden or working with the one you already have, it is always useful to sketch out the different areas of your landscape. To reduce water usage you will want to create different water-need spaces. Areas that will need the most water are likely to be vegetable gardens, flower gardens and lawns. Hardscapes (permanent features like patios, buildings and swimming pools) can have planters or potted areas that can be served with drip irrigation lines.
One you have different areas marked out on paper, you might want to spend a little time thinking about what you really need. If you have a lawn, will it be used? If it is there only to look good, can you reduce the size for the best visual impact and the least water consumption? Lawns are big water hogs. Vegetable gardens do use a lot of water, but they offer a big payback in return. Do you want a small vegetable garden? Do you want something larger to preserve produce or share with a number of people? Fruit trees also offer a big bang for the buck by delivering ornamental flowers in the spring, fruit in the summer and foliage color in the autumn. Group your fruit trees in an orchard if you have the space for one. By clustering plants with similar water needs together you can water each area according to those needs and not waste the water where it isn't needed. If you want to grow showy flowers you will also need more water. Consider grouping these plants near the house where the effect will be the greatest or try setting aside a limited area for a (flower) cutting garden. The rest of the space can create a complementary design while using minimal water.
Grow areas of drought-tolerant plantings. Native plants are a great source for easy to grow choices. If they grow locally without any fuss, you won't have to fuss either. Chances are they will grow in the local soil with no added water since that is how they've naturally evolved. To make them more attractive than in the wild, you can design groups of the same plant in interesting color combinations or inter-planted with other plants with similar growing needs. One word of advice: plan on watering even the toughest of plants for the first year or two until the plants have grown a full root system and can support themselves on reduced water. (This is a great reason why it's smart to plant a drought-tolerant garden BEFORE water rationing or high prices go into effect!)
Make sure each area is getting only the water that it needs. With many watering systems the water runs off and never penetrates the ground. Check out your drainage. Sometimes rocky or sandy soils will drain very quickly. This means that there is likely to be very little run off and the surface will probably dry out quickly. If you have a heavy soil or a clay soil, it may be difficult for the water to sink in and the longer you leave water on, the more it will simply wash away.
Watering early in the morning will allow more water to sink into the soil rather than evaporate away into the daytime air. Watering on cloudy days will accomplish the same thing. Watering evenings will encourage fungus infections that will love growing in the damp dark of the nighttime.
So if you have fast draining soil, use drip systems for widely spaced plants or plantings and allow soil to moisten over a period of time so the water had a chance to get to the roots. Slow draining soil will need to be watered to saturation -- which may only be minutes --, rested, then watered again once or twice to allow the water to sink in before the next application. There are low-volume sprinkler heads on the market that will help deliver water slowly no matter what kind of soil you have.
In summary, to grow a really beautiful, drought tolerant garden, first you need to plan it, sketch it and think about what you are doing. Choose high water areas to be productive and useful and fill in the rest of the area with natives and other drought-tolerant plants. Make sure all plants have a regulated source of water that is dispensed where it is needed and slowly enough to seep deeply to the bottom of the root system. And feel free to add pathways, patios and other areas that will be attractive, useful and require no water at all!