This allows the grass to be in place for the earliest spring growth. Bluegrass seeds does require the soil temperature to be at least warm enough for germination and  root development for winter survival. This grass can also be seeded in late winter and early spring.

KENTUCKY BLUEGRASS

STEP 2- Measure and lay out your site - record the square feet lawn area that you have.  Different lawn grasses handle different aspects of your site in unique ways.  What may be a suitable site for some grass types is not suitable for others.  Allow for other types of shrubs and ground covers for use in the areas that are not suitable for grass to properly grow.

STEP 3- Pull soil samples and have a qualified laboratory test your soil for nutrients and deficiencies.  Then you will be able to fertilize correctly and make other soil adjustments as needed.  You can apply the adjustments before tilling so as to incorporate them uniformly.  Fertilizers are best applied after tilling but before dragging / raking the soil areas level.  You can also apply the fertilizers immediately after planting to Bluegrass lawn areas you have seeded. Do not over-fertilize if planting in the fall or as nitrogen can make your grass more winter kill susceptible.

STEP 5- There are two methods you can use to "kill" off your current lawn. The best method is to spray the lawn with a total kill herbicide product such as "Roundup" (Brand name of a glyphosphate produced by Monsanto) before you roto-till.   This ensures that the existing grasses and weeds will not stay around to compete with your newly seeded lawn plants. The second method is to just tiller (roto-till) the existing weeds and grasses without killing the plants with chemicals.  Be sure and wait the proper length of time required by the particular chemical you are using before planting seeds.  Read the label to determine this time.  Planting to early could result in your seedlings being injured or killed by residue chemicals.

STEP 6- Most likely you will need to tiller the lawn at least two times so as to incorporate the soil and old plant material uniformly.  This is especially true if you do not use a chemical to kill existing plants.  A good method is to till the lawn and then wait a week before tilling a second time.  This results in more "kill" of current plants in your lawn area.

STEP 7-  After tilling the lawn ... you need to drag and level the surface to provide for a clean, smooth and level surface to plant within.  Properly leveling your lawn now will help to avoid the lawn being scalped by your mower.
You can use a rake to do this step or for bigger areas some sort of heavy drag like device drug behind a tractor or riding lawn mower can achieve similar results.  Remove any clumps of weeds or grass left, and break up clods of dirt to create a fine seedbed in the top 3 inches of soil.