You can't do a marketing plan without getting many people involved. No matter what your size, get feedback from all parts of your company: finance, manufacturing, personnel, supply and so on--in addition to marketing itself. This is especially important because it will take all aspects of your company to make your marketing plan work. Your key people can provide realistic input on what's achievable and how your goals can be reached, and they can share any insights they have on any potential, as-yet-unrealized marketing opportunities, adding another dimension to your plan. If you're essentially a one-person management operation, you'll have to wear all your hats at one time--but at least the meetings will be short!
The benefits of Marketing Plan, including: to achieve better coordination of activities. To identify expected developments. To improve the organization's readiness to change. To minimize the irrational response to unexpected responses. To reduce conflicts about how organizations should move. To improve communication. To urge management to think systematically. To expand the adjustment of existing resources to elicit preferred opportunities.