Spread a commercial herbicide over the entire area about a month before you plan on planting your grass seed. Weeds will sap nutrients from your grass and inhibit its growth, so you need to kill them before you put any grass seed down. Wait three to four weeks before planting grass.
Test the pH level of your soil. Soil test kits are available at hardware stores, home improvement stores, garden centers and nurseries. Follow the instructions included with the kit and record your findings. The soil should be between 6.0 and 7.5.
Cultivate the soil. If you have a lot of area to cover, use a rototiller. If your lawn is small, use a garden fork or rototiller to break up the soil. Amend your soil with either sulfur or lime, depending on the results of your pH test. Sulfur will lower the pH level and lime will raise it. Follow the instructions on the packaging for specific amounts to use based on the initial pH level and the area of your lawn. Spread an all-purpose lawn fertilizer over the soil. Blend the soil amendments into the top 6 inches of the soil with your rototiller or garden fork.
Rake the soil to make it level and to gather any rocks or other debris that may interfere with the growth of your grass. Discard the rocks and debris.
Fill a seed spreader with an appropriate amount of grass seed. On average, about 1 lb. of grass seed will cover 250 square feet of lawn. Lightly water the soil so that the top 1 to 2 inches are moist. This will help prevent the seeds from blowing away. Spread an even layer of grass seed over the soil.
Water the grass seed gently to keep it from shifting around too much. Water the grass seed three to five times a day until it sprouts. Once the grass sprouts, reduce watering frequency to twice a day. When the grass is about 3 inches tall, reduce watering to once a day. Water first thing in the morning so that the grass can stay moist throughout the day.