Test your soil's pH. If it is between 6.5 and 7.0, then it is at its optimal pH for natural growth. This pH will also prevent weeds from popping up. If your pH is any lower than 6.5, sprinkle some lime, according to the manufacturer's directions to correct the pH.
Amend the soil to form a loamy, nutrient-rich type. Loam soil has an equal amount of sand, clay and compost to help the soil breathe. This will ensure optimal root spread that will choke out weeds.
Water your lawn deeply, irrigating with 1 inch of water weekly. This ensures the grass's roots go deep for their water and produce healthy stalks.
Fertilize regularly with a balanced lawn fertilizer. Neglecting proper fertilizing will result in the grass removing all nutrients from the soil making future planting and germinating more difficult.
Walk through your lawn and shake the grass to release the seeds as they form.
Wait for the new seed to germinate making your yard thicker.