This is an accidental post, written in response to an email from one of my How To Write Fast students:
You might check out this TED talk, though it is for a strategic call to action.
And I found this not-too-bad page on outlining speeches.
The simplest call to action is one where the speaker/author has power and the action is already specific and measurable. The only real requirement then is absolute clarity (like a process diagram), with specifics on roles, timings, and what constitutes a satisfactory deliverable.
Things get trickier when the exact actions are less specific and when the accountability is lower. In these cases, the call to action speech or document must be increasingly persuasive. This may be the hardest sort of nonfiction writing, but here's what I keep in mind:
Know the audience and write the first draft to a specific person (the one person you would most want to have act), if possible.
Knowing the audience means using the right vocabulary, knowing what is appealing and interesting to that person, knowing what is already in that person's head about the subject, knowing what the points of resistance are, and knowing what will make it personal. You also need to know how that person is engaged and persuaded - logic, stories, images, whatever.
Know how tough a sell this is. How difficult action will be. How much resistance, hostility, and skepticism is out there.
The opening needs to grab attention and create a mood. It needs to put people into the right emotional space and make distractions and vagrant thoughts disappear.
The person needs to see how this is in their interest. It needs to touch on the right levels of Maslow's hierarchy of needs. Stories, visions, evidence, and logical arguments may be used. Examples, including recognizing people in the audience specifically, may be helpful. Calling upon experts or getting testimonials can help, too. Questions and answers can be used at the end or within. Call and response is another technique.
Always make the benefits of success clear. Anything from a few extra bucks to the promised land.
What people often miss, especially execs, is the need to show support. This goes beyond "I'm behind you 100%." Tools, places to go for help, deferring other work, mentors, and more should be part of the talk (or included in a ready reference) because no one who thinks they are incapable of taking the action will make a real effort.
And it is best to have the motivation be intrinsic and positive. Otherwise, there is the danger of people gaming the system or even of malicious compliance.
The ending of the communication especially must be rousing, with reminders of what went before to make the case and the call to action stated clearly. In some cases, it may be important to have people publicly commit themselves to action at the end.
Overall, you need to keep that person's attention, keep the messages clear, involve the head as well as the heart, and make in memorable. To act, a person must understand what must be done (including the deadline and level of quality), be committed emotionally to doing it, have the necessary time, tools, and capabilities.
Does this help?