Drip irrigation system is known to be 75% more efficient than conventional irrigation systems. Install this system in your garden. You can also make a home made drip irrigation system. Fill a large can with water with few very tiny pores at the bottom and place under a plant. This is shown in the picture. Another good option is to get a gardening water can as it gives you control over the flow of water. Sprinkler systems waste a lot of water.
Water your plants in the cool of the mornings so that they absorb water before the sun dries it out. When you are watering, soak up your plants totally for once and then give a break. Do not adopt the strategy of frequent but little watering which is not very effective.
Types of plant:
Go for plants that are adapted to your climate and are native to your area. They will not ask for as much water as foreign plants. If you really want to reduce the water consumption, grow plants which do not use much water and have dryness resistant properties. You do not need all that grass in the garden, cut it short to a practical size and concrete the rest of the space. You can also increase the water retention capability of your soil by mixing it with water retention gels. However, it is only possible for limited soil volumes like in tubs and pots.
Growing plants in pots reduce water wastage as they hold water for long. Install a water butt to your roof drainage system and link it to a pipe in your garden so that rainwater goes under the plants and not into the drainage system. Storing rainwater and using it for irrigation is another way to conserve water.