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.
But, before we continue, we must understand and accept that steps of the marketing plan are universal. It is a logical approach of the planning activity, no matter where we apply it. The differences you meet from a plan to another consist in the degree of formality accorded to each phase, depending on the size and nature of the organization involved. For example, a small and not diversified company would adopt less formal procedures, because the managers in these cases have more experience and functional knowledge than the subordinates, and they are able to achieve direct control upon most factors. On the other hand, in a company with diversified activity, it is less likely that top managers have functional information in a higher degree than the subordinate managers. Therefore, the planning process must be formulated to ensure a strict discipline for everyone involved in the decisional chain.