Failure to clearly define and understand your market, your customers, and your customers' buying habits. Who are your customers? You should be able to clearly identify them in one or two sentences. How are you going to reach them? Is your product or service seasonal? What will you do in the off-season? How loyal are your potential customers to their current supplier? Do customers keep coming back or do they just purchase from you one time? Does it take a long time to close a sale or are your customers more driven by impulse buying?