At some point, you may move into a home with a tired, worn lawn. Before you decide that you need to remove it and start over from scratch, see if it can be renovated.
As a first step, just give the lawn good care. Check for diseases and pests and control any you find; get rid of weeds. At the best time of year for the type of grass, dethatch and aerate, being sure you do a thorough job: you want to be certain that grass seed will be able to reach the soil to germinate. Rake up and remove all debris.
Buy a grass seed compatible with your climate and the use the lawn will receive. Apply both seed and a complete dry granular, controlled-release fertilizer over the lawn. Topdress the area with an organic amendment such as compost or soil conditioner; it will seep into the holes made during aeration, improving the soil, and will also provide some protection for the germinating grass seeds.
Water the lawn lightly and evenly; then continue to water often enough to keep it constantly moist until the seeds are fully sprouted and the new blades are about one-third taller than their optimum height (this usually works out to 2 to 3 inches tall). You may need to water 3, 4, or more times a day if the weather is warm. Once the new grass is tall enough, you can mow it, taking off only the top third. At this time, begin a regular watering program, but avoid walking on the lawn for another 4 to 6 weeks.