Water, water, water.
It is critical that you water your lawn every day the first week. NEVER let the roots dry out!
HINT: Dry is bad, mud is bad. Moist is good.
Week Two: Reduce watering to every other day.
Mow after 10-14 days.
Never remove more than 1/3 of the grass in one mowing.
Start it out right.
• After four weeks apply a starter fertilizer.
• Keep it green and healthy by using a maintenance fertilizer something like a TurfBuilder, there are some organic options that are great as well.