Utilize your Defined Target Market to determine what kind of marketing you will put in place, and where you will advertise.
Where will your marketing efforts best reach your target market? If you want to reach Gen X - Facebook. If you want to reach Baby Boomers - run a radio ad or newspaper ad. Think about where your target market will be, and how they are most likely to see your ad.
The key to developing a detailed action plan is to maximize the results of your advertisement or marketing campaign for the least amount of money. You may be willing to spend $10 on marketing per Widget sold, but if you only have to spend $2 - that is more money you've retained as profit.
Your action plan should be specific and include what type of marketing campaign(s) you're going to execute. Online, Print, Out-of-Home. Radio, TV, Events, Tradeshows, direct-mail?
After you've defined the type - you should define the specific channels. Where online are you going to market - Facebook, your website, a blog, Google Adwords? What advertising will you run? Newspaper - which ones? Magazines - which ones? Radio - what stations?
Do this for every campaign type and develop a message that you want delivered within each campaign. Your message could be one main message or a variety of similar messages, or messages that are complete different depending on the type of campaign and targeted audience.
You will likely run ad campaigns with a different messages if you have a different target audience. The message attached to a campaign aimed at new Widget wholesalers will be different from the campaign for generating new retail customers.