You can help speed along the process with these four simple steps:
1 Water thoroughly.
2 Fertilize. After about two weeks of watering, use a broadcast spreader to apply a balanced fertilizer with proportions as close as possible to 4-1-2 for nitrogen, phosphorus, and potassium.
3 Kill weeds. Once the grass is growing strong, treat individual weeds—not the entire lawn—with an herbicide. By eliminating weeds, there will be more moisture and nutrients available for the grass. And as the lawn thickens, it'll eventually crowd out the weeds on its own.
4 Return to routine maintenance. Resume your regular lawn-maintenance schedule, which should include consistent watering, mowing, thatch removal, and aeration.