When I ask entrepreneurs and small business owners, it is not unusual for not having any marketing plan. I once read that Sir Richard Branson never had any marketing plan when he started the 1st Virgin business many years ago. In fact in one study of entrepreneurship (I couldn't recall the name of the study) was that as much as 50% of entrepreneurs and business owners don't have a business plan and marketing plan when they first started the business.
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.