Most lawns require one to two inches of water a week. The best way to water, especially to conserve water or if the lawn is on a slope, is to water for 5 minutes on and 15 minutes off, until the desired amount of water is delivered. This gives the water a chance to soak in and reduces runoff.
To determine if you are delivering the proper amount of water, place a few cans around on the lawn to catch the water. Use something that has straight sides so you get an accurate measurement. Tall cans can deflect water, so it is best to use short cans like tuna or cat food cans. Measure the water in the cans and multiply by the number of times a week you water. The result is the number of inches of water being delivered every week. Each can should yield about one to two inches per week depending on temperature, shade and type of grass. Sunny and warm locations will need more water. Remember to include any water from rain in your calculations.
To recap, the best way to water is in the morning, two to four times a week, in short intervals but enough to thoroughly soak the ground. A sprinkler system is the best way to deliver the water because it consistently covers the entire lawn and it can be programmed to deliver the water when and as frequently as needed.