Watering is the most critical step when trying to establish (root down) your new lawn.
Start watering your new lawn within 30 minutes of installation. You want to give it about 1 inch of water. Keep watering at least 2 to 4 times a day keeping the sod moist. The length of time to water will depend on how hot it is. If it is the middle of summer and the days are hot, then give your new lawn some extra water in the afternoon to cool it.
An easy way to tell if you are applying the right amount of water is to pull a piece of the sod back and check the moisture content. The sod and soil should be moist. If you take a hand full of soil and squeeze it, it should stick together. If excess water squeezes out, you are watering too much. If the soil does not stick together, you need more water. Another trick is to just look at your lawn; if it looks dry then it probably is. If it looks nice and moist, your watering schedule is probably right on track.
Keep watering on this schedule until the sod has rooted down. If you can't pull the sod up, it is rooted down. After it is rooted your sod should take less water. Water deeper (6 to 8 inches) and less frequently.