Prepare the planting area to loosen up the thick clay soil and promote root development. Remove debris and till to a depth of 4 to 6 inches. Spread 12 oz. of hydrated lime per square yard to make the clay take on a more neutral pH.
Make the clay more fertile with sand and compost. The substances will improve drainage, dry it out a bit and add air pockets.
Use a starter seed fertilizer to balance the nutrients in the clay dirt and help the seed root more quickly. Broadcast the seed evenly over the area with a spreader. Keep the soil moist until the grass sprouts, but avoid overwatering the clay because it has a tendency to hold onto moisture.