The first step in renovating a lawn is to do a soil test. Measuring the level of nutrients, especially nitrogen, in your soil will indicate what kind and quantity of fertilizer will be necessary. Specific types of grass require the soil to be within a specific pH range. Testing for soil chemistry for pH may indicate the need to adjust that balance with lime. Rutgers Cooperative Research and Extension has prepared a series of fact sheets, including this one on Soil Testing (PDF).