Rake the soil thoroughly. In order for grass seed to find purchase in your soil, you will need to till the soil up. If your soil is very poor or dry, you may need to use a garden tiller to turn up enough soil. However, in most yards a simple, thorough raking will suffice to turn up the soil.
Apply fertilizer to the soil. This will help provide your soil with the necessary nutrients for your grass seed. You can use a combination of animal manure and compost if you prefer, or a commercial blend of lawn fertilizer.
Let the fertilizer sit for a week. If you plant the seed on newly fertilized ground, it may actually kill off the seed. It is best to let the area sit for a week to allow the nutrients to soak all the way into the soil.
Re-rake the area and water it lightly. This will turn up the soil again and help it be more receptive to your grass seed. Once you have finished raking, water the soil lightly until it is just moist but not boggy. You do not want to have standing water in spots. Watering before planting your grass seed will help the seeds germinate, while watering after you seed can actually wash the grass seeds away.
Grab a handful of grass seed and shake it over the area to distribute the seed. Pay attention to how much you are spreading and adjust as necessary. It is better to over-seed an area than under-seed it.
Lightly water the newly seeded area daily. Again, you don't want to overwater but the seeds will need a moist environment to germinate properly. If your soil stays moist, you won't need to water much. Do this daily until your seeds start to sprout.
Avoid premature mowing. Allow your newly seeded grass to reach a height of 3 to 4 inches before mowing, to avoid killing it off. Grass seed needs time to thoroughly establish itself before being cut.