You need to know everything obtainable about your customers. This list will get you started. You will need their age, sex, marital status, income levels, education levels, geographic locations, where they shop, if they go to church, if they have kids, ages of children, political affiliation, what they like about your company, what they don't like, why they shop with you, what they value about your products/services, what they like the most/least about products/services, and whether prospects are unaware of your brand or products/services. Customers want you to know certain things about them and if you do, they will remain loyal to you as you take time to know them.
Next determine who your market really is. You may end up having two market demographics: one for the product and one for the opportunity. Develop a market plan for each demographic. Not everyone is an entrepreneur but they may still be interested in the product. This is why quality is key. The product has to be able to stand on its own without the opportunity. Not everyone is going to be interested in the product. Try to narrow down the demographics of those that would be interested so that you can communicate more receptively with your market.