Mow the lawn for the first time in a month after overseeding. The lawn needs to be watered deeply for at least one week before mowing. Mow the lawn so that the clippings are not very long. This will help the lawn stay green and look better. If you do not have a mulching mower, you can use an edger. Edgers are used to cut grass into small pieces that are easier to compost. The grass will decompose faster if it is in small pieces.