Who should see your plan? All the players in the company. Firms typically keep their marketing plans very, very private for one of two very different reasons: Either they're too skimpy and management would be embarrassed to have them see the light of day, or they're solid and packed with information . . . which would make them extremely valuable to the competition.
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.