[header] How to forecast sales before starting a business [title] Identify likely customers. [step] Work to define a market for your product or service. Who do you expect will have the desire and the money to purchase it? Using demographic information, define the characteristics of your likely customers. 
Demographic characteristics include age, sex, marital status, income, children, and other characteristics as you see fit. The more you know about your customers, the more likely your projections of sales will be correct.