According to Richard Jauron of the Iowa State University Department of Horticulture, the appearance of moss in the lawn is a symptom of an underlying problem. Most of those problems involve too much moisture in the soil, such as poor drainage, need for aeration or too much shade cover. While the moss itself is simple to review, stopping it from growing again takes a bit more effort and investigation into the cause of the problem.
Rake up the existing moss using a leaf rake. Remove as much of the moss as possible without damaging the grass or ripping away too much of the soil.
Prune low-hanging branches and upper branches in trees that block significant amounts of sunlight. If moss is growing mainly in areas around bushes and trees, the problem may be lack of sunlight, leaving the ground too moist.
Aerate the soil using a home lawn aerator. The process will help loosen compacted soil, improving drainage and making it more difficult for moss to grow. Since compacted soil doesn't drain as well, it can become soggy, creating an ideal atmosphere for moss.
Inspect the lawn for areas that aren't draining properly. Lines of moss or areas with standing water or that are soggy are signs of poor drainage.
Dig small drainage trenches as necessary to improve lawn drainage and eliminate standing water. Line the trenches with stones or tiles if desired to keep soil from washing away and approve the appearance.