Collect soil from several areas around the new lawn site. Mix the soil together and allow to dry. Deliver the soil sample to your local agricultural extension service for analysis.
Cultivate the new lawn site with the rototiller. Rake and remove all errant weeds, roots and rocks from the area. Work the soil to a final cultivated depth of at least 6 inches with the tines of the rototiller.
Add the correct amounts of organic soil amendments and lawn fertilizer based on the soil test results. Incorporate the material into the soil with the rototiller.
Grade the soil surface with the garden rake so all water runs away from current structures. Fill in all low-lying areas so water won't puddle. Standing water kills the grass seed and young seedlings.
Broadcast the grass seed according to the label directions on the package. Different types of grass have various seeding rates. Run the garden rake over the seed to cover lightly with soil.
Mulch the new seed with one-year-old straw mulch to retain moisture and hold the seed in place. One small square bale will cover 1,000 square feet. Irrigate the new lawn area to keep it from drying out.