Tip #1:
When putting down fertilizer, it's best to do so when the grass is slightly damp. Early morning, or just after a light shower are both good times. This will help the fertilizer and/or weed killer cling to the blades of grass.
Tip #2:
Water your lawn regularly, but not for too long. A good rule of thumb is to move your sprinkler as soon as water begins to pool on the surface--after about 15 to 30 minutes.

Tip #3:
Don't cut your grass too short. In the heat of the summer, the shorter your grass, the faster it will dry out and become discolored.