Lawn mowing is more time consuming than any other lawn-care practice. Regular mowing with a sharp mower blade at the proper height will help keep grass growing vigorously and maintain adequate density. Proper mowing practices contribute to a healthy lawn and minimal 
weeds, and, if you leave grass clippings on your lawn, contribute
For a typical residential lawn, maintain a height of 3 inches or higher. Taller grass shades out weed seeds and keeps soil cooler. Taller grass means longer roots and greater ability to withstand drought and reach nutrients. Remove no more than 1/3 of the leaf tissue when you mow.
Mowing too short or scalping results in stress to the grass plant. Weak grass plants will take longer to recover. To maintain a 3-inch lawn, mow before the grass reaches 4.5 inches tall. Mowing too short can allow weed seeds to get more sun and increase the chance of germination.
Finally, leave your clippings on the lawn. Decomposed clippings add the equivalent of one fertilizer application to your lawn each year. Decomposed clippings improve soil quality and minimize runoff.