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.
The marketing plan is the overview of multi_channel approaches you should be implementing to develop and retain your prospects. It may include a call for brand development and demand generation as well. If your existing strategy is somewhat successful, but you want to grow _ the marketing services it recommends may be more focused on customer relations _ such as social media marketing, email marketing and telemarketing services.