Rake any dead or dying grass from the affected areas as the weather begins to make its transition from summer to autumn.
Examine your grass to note which type is growing. Grass may be hot- or cool-weather grass and fescue or rye. Mixing a different type of grass in with an established lawn will create areas that look a little different from the rest, and which might need a different type of maintenance.
Cut the grass over the affected areas at the shortest setting the lawnmower will allow.
Scatter a mixture of starter fertilizer with 1/2 inch of top soil throughout the affected areas to give the grass seed a place to establish its roots.
Broadcast the grass seed with a spreader if the area is wide. If it is a smaller, localized area then just ensure the grass is well-spread by hand.
Tamp the seed into the soil to give it good contact, or smooth the area with the back of a shovel. Water lightly and continue to lightly water every day until the grass begins to sprout.