Ideally, after writing marketing plans for a few years, you can sit back and review a series of them, year after year, and check the progress of your company. Of course, sometimes this is hard to make time for (;there is that annoying real world to deal with);, but it can provide an unparalleled objective view of what you've been doing with your business life over a number of years.
Firms that are successful in marketing invariably start with a marketing plan. Large companies have plans with hundreds of pages; small companies can get by with a half-dozen sheets. Put your marketing plan in a three-ring binder. Refer to it at least quarterly, but better yet monthly. Leave a tab for putting in monthly reports on sales/manufacturing; this will allow you to track performance as you follow the plan.