Mow Height is the most important aspect of maintaining a healthy lawn.  Mow high and mow often is the rule.  Instead of mowing your lawn on the same day every week, change your habit to mow your grass when it reaches 3 to 3.5 inches.  And then only mow it to a cut height of 2.5 inches. By taking no more than 1 inch off the blade of grass, the plant remains strong and healthy. By keeping the grass tall, it is able to shade and choke out weeds, and has sufficient blade surface for photosynthesis to maintain its health.