Small yards or areas with minimal thatch may simply be raked with a leaf or dethatching rake. However, larger lawns and those with more than an inch of thatch must be dethatched with a power dethatcher. Power dethatchers can be rented at many home improvement stores and they work much like lawnmowers with vertical as opposed to horizontal blades.
However, while power dethatchers will dethatch a lawn with minimal effort, they can also do a lot of damage. Therefore it's best to dethatch at the beginning of your grass' growing season to reduce recovery time.
Cut your grass to half the height that you normally keep it.
Remove any lawn debris like leaves, twigs or stones.
Rent a power dethatcher with an engine that has at least 7 horsepower.
Calibrate the depth and spacing of your blades. The clerk who rents you the dethatcher (or the manual) should be able to help you with specifications based on the type of grass that you have.
Dethatcher blades are usually set to cut into the top half inch of the soil. Blade spacing will largely depend on the type of grass you have. Tough warm season grasses like Bermuda need one to two inches and thinner grasses need three or more inches of space and increased blade height.
Lightly water your lawn. Damp thatch is more easily removed.
Run the dethatcher over your lawn according to the manufacturer's instructions. If you have to make more than one pass over an area, be sure to make the second pass at a ninety degree angle to the first. This will ensure that you don't pull up your grass along with your thatch.
Remove all of the dislodged thatch from your lawn with a leaf rake.
Fertilize your lawn with a 3-1-2 or 10-10-10 fertilizer according to the manufacturer's instructions to help your lawn recover more quickly.