Sow bluegrass, fescue, or bent grass in August or September, when there are several weeks of cool weather before freezing.  Because perennial ryegrasses grow quickly, you can plant them either in the fall or during the first favorable spring weather when the soil is not too moist.

To be sure of success when seeding a new lawn, choose a high-quality seed mixture containing very little "crop" (weeds).  The package should also list the purity of desired cultivars.  A good mixture containing mostly bluegrass, some fine fescue, and a portion of perennial ryegrass will be able to contend with most of the weeds your lawn contains.  When buying seed, you get what you pay for: a more expensive seed will more than make up for its price by the quality of lawn it produces.

Before planting, prepare the soil-bed properly, so the surface is cultivated to marble-size soil clods.  Then, broadcast seeds with a mechanical spreader, following the package instructions for the correct amount of seed per 1,000 square feet.  Mix the seeds in the hopper before spreading.

If the soil surface is ideal, seeds will fall into cracks and crevices between the soil aggregates, where they will germinate.  When planting on a slope, work across the slope--not up and down--so grass seed will not wash away when you water it or when it rains.  Avoid planting seeds too deeply or they may not come up at all.  If soil is sandy or powdery, though, roll the lawn just once to firm up the seed.

Mulch will help protect new seedlings and keep them from washing away.  Use straw, burlap, nylon mesh, or other suitable materials.  Water the newly planted lawn often, but lightly.  When new seedlings are about two inches high, they're ready for their first mowing.