Test your lawn for pH and nutrient levels. You can get a testing kit from most university extension offices. After you take a sample of the soil with the soil kit, submit it to the extension center and wait for the results.The test will give you a recommendation about your soil and the soil nutrients in addition to a recommendation for what type and amount of fertilizer you should use on your yard.
Chose between an organic or synthetic fertilizer. While the plants can't tell the difference between the two, there are a few issues to consider. Although organic fertilizers are less likely to cause burns than high-release synthetic fertilizers, a controlled-release synthetic fertilizer usually will not burn. You may need more organic fertilizer to supply your yard, as the nitrogen percentages can be low in organic fertilizers. And don't mistake organic materials such as compost as necessarily being better for your soil. While it may increase the quality of the soil, it does not increase the soil's nutrients.
Select a fertilizer that will best work for your yard. You can read the bag by looking at the three numbers. The first number represents the percentage of nitrogen. The second number represents the percentage of phosphorous, and the third the percentage of potassium, as in a 20-3-4 bag of fertilizer. If your yard falls into a medium, balanced category, you should select a 20-3-4 or 26-3-5 fertilizer, which means that your soil needs more nitrogen than phosphorous. If your lawn is low on phosphorous, you should select a 13-13-13 fertilizer, which provides equal parts nitrogen and phosphorous. You will almost never need a large percentage of potassium unless your lawn is seriously deficient. However, you should have at least 1 percent, because potassium helps prevent disease. For a new lawn, you may want to select a starter fertilizer, such as a 18-24-6.
Chose a slow-release liquid fertilizer, especially if you have a large area to fertilize and you require a higher percentage of nitrogen. A slow-release fertilizer will prevent your lawn from burning due to the application of nitrogen. It will also help balance the nutrients in your soil over a longer period of time.