Deep watering is key. It promotes root growth which will protect the grass from extreme heat during the hotter months. Roots will only grow where there is water.
I used to water for 20 mins every 3rd day and occasionally throw down some cheap fertilizer (Ammonium nitrate...I think...or was it sulfate
). It is a quick release, so be careful because one can easily "burn" their grass if too much is put down.