Aerating a lawn loosens compacted soil. Aerating tools are designed to lift a small core out of the soil and release it onto the top of the grass. Aerating improves drainage, controls weeds and thatch, and allows water, fertilizer and air to reach the roots of the grass. It is easiest to aerate a lawn after the ground has been thoroughly saturated with water, so wait until the day after it rains, or completely soak your lawn the day before you begin to aerate. Also, mark sprinkler heads or other hidden items such as drip irrigation systems with flags so you don't accidentally "core" them with your aerator, especially if you are using a mechanical one. Aerate your lawn in the fall every 2 to 3 years to keep your lawn in optimum condition.
To aerate your lawn, use your foot to press the aerating tool firmly into the soft ground. This motion is very similar to if you were pushing a shovel into the ground. Then, pull up the core of dirt and release it to lie on the grass. Most aerating tools have a hand lever that releases the plug of dirt from the tool. Continue to aerate, following the same path you do when you mow the lawn. Your holes will be about 4 to 6 inches apart, depending on the size of your aerator. Manual aerating tools allow you to get into tight corners and are effective for most normal-sized lawns. If you have a lot of land, however, you might want to consider renting a mechanical aerator.
After you are done using the aerator, sprinkle fertilizer, seed or both over the lawn. Then, use a rake to dissolve and spread out the cores of dirt that you left lying on the grass. Although this will naturally fill in some of the holes, do not worry about filling every hole. The grass will cover the holes in a very short time. Finally, water your lawn thoroughly after you have finished raking.