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.
Resource Plan _ in marketing, there is only one thing that's scarce: RESOURCES. Some people have a lot of money but lacked ideas and another group is the other extreme; more ideas and less money. Many of us probably the later than the former! In the marketing plan we will tackle things like people to hire, pricing, distribution plan, sales programs budget and so on.