Prepare the Lawn for Aeration
Water the lawn thoroughly one to two days prior to aerating your lawn. Apply at least 1" of water to the grass; this can be measured by placing an empty tuna can in the middle of the watering zone. If the can is full, then 1" of water has been applied to the grass. Watering the lawn will help the aerator penetrate the soil and pull out soil cores much more easily. Flag irrigation heads and other hidden objects in the lawn so that you will avoid them when operating the aerator over this area. If you do not have an irrigation system, use a garden hose and sprinkler to water the lawn.
Note: Depending on your climate, the best time of the year to aerate cool-season grass, such as fescue, bluegrass or rye, is in August through October when the grass is breaking its dormancy and begins the period of active growth; the best time to aerate warm-season grass, such as Bermuda, Zoysia or St. Augustine, is April through June.