It's intimidating and overwhelming. Just the idea of thinking through a huge chunk of time and deciding everything that is going to happen is a lot to handle in the midst of your other assigned responsibilities — Not to mention the idea of creating a print and digital document that holds you and others accountable to it all.
Like most things that make us break out in hives just, if we break it down into parts, it's a lot more manageable. Think through your planning process backwards. Start with the end in mind and work your way to today. Like this....
1. What do you want to accomplish by what date? (I want to sell 100 doohickies in the next six months.)
2. Who is your audience: target and secondary? (Dads are target, moms who are buying for dads are secondary)
3. What value will your buyers derive from your doohickie? (A gadget that makes life a bit easier and raises their "cool factor")
4. Where does your audience exist—home, work, online spaces, social spaces? (upper middle class neighborhoods, white collar jobs, read "Wired" magazine and frequent Facebook)
5. What tools will you use to reach them — print, advertising, online, social, video, events, etc... (advertising in Wired, PPC through Facebook and Google Adwords, video content, strong branding)
6. When is the best time to get them to buy? (right before the holidays, moms are looking for good ideas for dad)
7. How much does reaching them cost?
A marketing plan, at minimal, clearly defines all of these things. From there, make a calendar with tasks and assign people to each task. Share it with the right people. Make sure you have a person in charge of accountability and then GO!