Raking/Dethatching:
The 1st step in preparing your lawn for spring is to clean up any debris that is lying around the yard (sticks, leaves, plow damage, thatch, etc).
Thatch is a layer of both living and dead grass shoots/roots/stems that builds up between your soil and grass blades that can be eliminated by raking or dethatching your lawn (see below).
Rake as many times as needed to achieve a thatch layer of ½ inch or less or hire a professional landscaping company to do this for you. Anything greater than ½ inches of thatch can be unhealthy for your lawn.
A thick layer will restrict the amount of nutrients and water that your grass roots will be able to absorb.
Raking and dethatching can begin any time after your snow season is complete.