Preparing the yard is the most important factor when planting grass seed. For best results, remove anything that can get in the way of the seed germinating. Seed needs direct contact with fertile soil to develop roots. Plan to spend one or two days preparing the site and dispersing grass seed. It should be done in dry weather, without wind to contend with. Plant grass seed in the spring or early summer to ensure it begins to sprout before cold weather arrives.
Remove debris such as branches and rocks. Soil clumps larger than 1 inch across should be broken up.
Pull weeds by hand. Try to remove the roots, too. Use an herbicide several weeks before planting grass seed if you have a large weed problem. Applying the weed killer too close to planting time will kill the grass seed, too, so be careful.
Dig at least four inches into the ground with the rototiller. Loosen up the soil to make air pockets. This gives the roots space to spread easily.
Level the planting area. Put topsoil into dips and crevices to fill them in. Smooth it out with a rake.
Make the soil more fertile and improve drainage. Add one inch of compost and one inch of sand. Mix them into the top of the soil with the rototiller.
Fertilize the soil with a started seed blend. It should be high in phosphorus which encourages root growth. Follow the manufacturer's instructions to determine the rate for the broadcast spreader.
Fill a hand spreader or mechanical spreader with the appropriate amount of grass seed. Refer to the seedbag for instructions.
Gently run the back of the metal rake over the grass seed. Cover the seed with the top one-fourth inch of soil. This will keep it in place and help it germinate quicker.
Water the newly planted lawn with a sprinkler on the oscillating setting. Water for five- to 10-minute increments at least twice a day. Water more if your climate is hot. Stick to this regimen for 10 days, then cut down to daily watering for 15 to 30 minutes.