There's no need to water more than an inch per week. Over-watering is unhealthy for lawns and invites lawn disease. Placing a tuna can under the sprinkler will help gauge water depth. Water early in the morning to avoid excessive evaporation from midday sun.
Taller grass has deeper roots, causing the plants to need less watering. Set mower height to 3 inches and cut grass when it reaches 4.5 inches. Sharpen mower blades. Dull blades harm grass blades, inviting disease.
Return grass clippings to the lawn. Grass mulching decreases weeds up to 60% and is a natural fertilizer.
Avoid cheap grass seed, as it typically has weed seeds mixed in. Get good quality perennial rye and fescue seeds.
Each time you mow, try alternating your pattern and path. This prevents the soil from compacting.
Soil biota helps provide a stable healthy lawn. If your lawn has been treated chemically, it will take a couple of years for the soil microorganisms to rebuild.