Let us see what do we call a "marketing plan"? It is the result of the planning activity, a document that includes a review of the organization's place in the market, an analysis of the STEP factors as well as a SWOT analysis. A complete plan would also formulate some presumptions on why we think the past marketing strategy was successful or not. The next phase shall present the objectives we set, together with the strategies to achieve these objectives. In a logical sequence, we will further need to evaluate the results and formulate alternative plans of action. A plan would consist in details of responsibilities, costs, sales prognosis and budgeting issues.
You must know your competition in and out. Keep your friends close, but keep your competitors closer. You need to know all the things that you learned about your customers except fill in the blank for each competitor on all of those above items. Learn how you are the same/ different. Learn the similarities/differences about each product and service you offer. Learn how they sell or promote their products /services.