Here are two critical things you should know about your business. First, what percentage of customers or clients defect every year? This tells you how much new business you need each year simply to stay where you are. Second, why did they leave? Are there changes you can make to prevent further defections? If the answer is yes, you need two plans: one to fix what needs fixing, and one to let customers know about the changes. Done correctly, you can even woo some of the lost customers back to the fold.