Plant grass seed in the autumn to reduce competition from weeds and other plants, and choose a seed variety that is recommended for your region to ensure the grass thrives. Before planting, perform a soil test, and amend the soil according to the results of the test. Work compost, sand and fertilizer into the soil before seeding a new lawn, and aerate existing lawns to promote healthy new growth. Water both new and existing lawns heavily after planting the seeds.
Do not apply herbicide to the lawn after planting grass seed. To remove weeds, use a recommended herbicide, and read the product packaging to determine how long to wait before planting grass seed. After mowing the grass four to five times, resume using herbicide as needed to control weeds.
To thicken sparse grass, overseed the lawn by broadcasting grass seed in the desired areas after aerating the lawn. If thick grass is present, use a slice-seeding method to apply the grass seed, as slice-seeding places the grass seed directly in the soil.
To renovate the lawn, remove old sod with a sod cutter, and till the soil. Add sand and compost as needed to reach the desired soil type before planting the grass seed. Water the lawn lightly several times each day until the grass is well-established.