Till the soil. Using a rototiller or lawn tractor may be the most efficient option for large areas, but avoid working in wet conditions. Driving or walking on wet clay will further compact the soil.
Identify a source of organic matter. Organic matter, such as compost and rotted manure, will improve your turf success by encouraging biological activity and giving the soil a looser, more porous structure. Plan for enough material to cover the entire area approximately 1 inch deep.
Inspect the organic matter. Any compost used in turf areas should have a fine texture. This will provide a better growing medium for grass seedlings. Compost should be free of twigs, leaves and other identifiable vegetation. Particles should be less than 1/2 inch in size.
Test the soil. This will tell you whether you need to add other amendments in order to correct pH and other nutrient deficiencies. Testing your compost is also a good idea. If your compost is high in available nitrogen, you will need less of it.
Spread the organic matter. Apply the material 1/2 to 1 inch deep. Make sure to apply it evenly to prevent low spots later on.
Till the organic matter into the soil. Work the material into the soil approximately 6 inches deep.