The fastest way to grow grass is to have the lawn sodded. It's an instantaneous lawn. One day you're looking at dirt, the next day a lovely green yard. Growing grass by seed can be accelerated depending on the outdoor temperatures and season. Warm soil and all but hot air temperatures are ideal for grass germination. If an ugly dead spot is ruining your otherwise lush lawn, the spot can be filled in quickly with new grass.
Prepare the soil. Dig up the bare or brown spots and remove the top 3-inch layer of soil to rid the area of contaminants such as fungus or dog urine that inhibit growth. Fill the depression with bagged topsoil. Tamp down the soil and water until the soil is wet to a depth of 3 inches.
Spread a handful of grass seed over the soil and press gently into the soil. Cover the seed with a 1/4 of an inch of soil from a part of the yard that is similar to the surrounding soil so it will dry out or retain moisture at the same rate. Water again with a light spray of water so the seeds are thoroughly soaked.
Cut a piece of clear plastic the same size as the area that was seeded. Spread it over the newly seeded area. Secure the plastic to the ground with wires bent into U shapes.
Check after a few days to see if the seeds have germinated. Remove the plastic as soon as the seeds have germinated.
Keep the new area watered well so the soil is damp to a depth of 3 inches. Water the seeds with a gentle spray so they don't wash away or become displaced.