To make an effective plan, there is a famous rule called 4P's. Here, P's stand for Price, Product, Promotion and Placement. In this another P is added called People. Today while doing digital marketing or the traditional marketing one should understand people or the customers you are dealing with. It's important to figure out what is significant for the business, and later make a plan accordingly.
Marketing Research will be the first component for your marketing plan. You may be doing this in house or you may elect to hire a top marketing agency, a marketing consultant, or maybe a specific marketing research firm. You need to obtain and capture all data about your business along with your products and services to help you properly facilitate any potential marketing problems. You may also be able to get some marketing data from an industry trade association or from other businesses within your specific industry.