It takes anywhere from a week to 10 days for the seeds to send up grass shoots. When working from bare ground, the advice I have read says that when these shoots are about 2 to 3 centimeters long, add another layer of grass seed and in approximately one month, you should start seeing some lush grass grow. Be sure to keep the area moist while new grass is growing in.
When planting a new area from seed, sprinkle the seed into newly tilled soil, then rake over the seeds so that they are covered with about 1-2 centimeters of dirt. Keep them well watered, but don’t overwater them, as you will drown the new shoots. Most grass varieties should be planted in the spring or fall. Common hearty varieties include Fescue, Bermuda and St. Augustine. There are very useful instructions in an article called The Grass is Always Greener.