When lawn soil is compacted, a lawn might not be getting the air it needs to thrive. Lawn aeration attends to this problem, pulling up plugs of soil and allowing water and nutrients to reach the roots of grass.
Lawn aeration strengthens the roots, and strong roots equal a lush, green lawn. Aerating once or twice a year will generally do, with a lawn aerator.
Use a lawn aerator that pulls out plugs of soil, not one that uses spikes. Since the spikes don’t take any soil out with them, they often contribute to the very soil compaction problem they are trying to solve for the lawn.
Water the lawn the night before you plan to aerate. This will ensure that all of the soil is nice and soft (Working a lawn aerator through dry, hard earth can be a challenge and back breaking work).
Aerate the highest traffic parts of the lawn most frequently. Heavy foot traffic can make soil practically impermeable, and lawn aeration can go a long way to solving high-traffic-area problems like slow growth and low resistance to wear and tear. Lawn aeration can make particularly weak lawns vulnerable to weeds, though, so consider applying an herbicide at the same time you aerate.
When the aeration project is done, simply gather up the plugs.