Turf grasses need soil temperatures around 60 degrees Fahrenheit to germinate. In many climate zones, this occurs twice during the year: in spring as the ground warms and in fall when it cools. Warm-season grasses, such as hybrid Bermuda, St. Augustine, centipede and Zoysia grasses, grow most actively during the warmest months and are best planted in spring. You can also plant cool-season grasses in spring but they will be set back if the weather turns suddenly hot or dry.
Cultivate your topsoil with a shovel and cultivator or rotary tiller in spring, when it has dried enough to crumble instead of clumping.
Add 2 inches of well-rotted compost and manure and work it into the top 6 inches of the soil to make a bed of well-drained, friable loam.
Level the area with a garden rake or a piece of 2-by-4 lumber dragged across the surface. Pick up rocks, weeds and root clumps as you go. Your lawn should slope gently away from buildings and toward drainage swales or storm sewers.
Water well and let the graded soil settle for a few days.
Choose a warm season grass seed or a cool season mixture that is appropriate for your area. Check with your local state university agricultural extension for help in choosing grass seed.
Seed with a drop or broadcast spreader (check seed package instructions or ask your nursery professional for proper spreader settings) when the soil temperature reaches 60 degrees Fahrenheit. In general, seed warm-season grasses from 1/4 lb. to 2 lbs. per 1,000 square feet of lawn; cool-season seed mixtures spread at between 1 1/2 lbs. to 2 lbs. per 1,000 square feet. Walk one way up and down the area to drop half of the seed, then walk again across the area for maximum coverage.
Cover the grass seed slightly by working a broom rake or your garden rake lightly around the soil surface. If nights are still very cool, mulch the seed with 1 inch of Canadian sphagnum peat moss or marsh hay.
Water the settled seed well and keep the ground moist by watering lightly each morning until seedlings begin to develop several blades.