Lime can help you keep balanced, or at least keep your soil balanced.  If you are working with soil that has a low pH balance, you are working with acidic soil.  Some plants will not thrive in this type of soil, so you will want to amend the soil.  That is where lime comes in. 

Neutral soil has a pH of 7.0.  Generally, you will only want to raise the pH if your soils has dropped below 6.0.  By working lime into the soil (lime the mineral, not the citrus fruit), you can make the soil more alkaline (balancing out the acid that is present).  You will want to work the lime into the first 8 inches of your soil to have neutralize the pH.  Lime can be purchased at your local garden center and at many hardware stores.