Most public education systems include a lesson or two in persuasive writing. The core concepts of that lesson can be applied to petitioning a local governing body, writing a cover letter for a job, or lobbying a board of directors for a business, nonprofit organization or public agency to make an important decision. Keep in mind, however, that there is a difference between trying to persuade just one person and trying to convince an entire board to see things your way.
Think with numbers. You'll need numbers to show that the cost of your proposed idea is not detrimental, or numbers to show that it will save the organization money. You'll need numbers, in the form of a survey, to illustrate that a community supports your idea. If writing a recommendation to hire, fire, promote or demote someone, you need numbers to show how productive or inefficient they were, or cite a number of people who share your opinion.
Document anecdotal evidence. The numbers are the bones, but the words are the meat. If a school board is contemplating a lighted football field, write about how Friday night games could become a proud community tradition; if you're against it, write how the games could become a haven for loitering and underage drinking. If the board is considering a new Chief Executive Officer, provide examples of leadership, charisma or other positive personality traits that you have personally observed or can attribute to a reliable source.
Play devil's advocate with yourself and write down what arguments opponents might make on your position-then come up with your response.
Start organizing your letter, writing the overview and the summary sections first. The overview should briefly touch on your strongest points, but not necessarily every point you will make in the body of the letter. The summary should repeat some key points, not necessarily those in the overview, and finish with a statement that is general enough to speak for all points made in the letter.
Compose in the body of the letter enough points and examples to strike a chord with each board member based on what you know about their background and positions on various issues. Keep the anticipated points of argument and your response short and near the bottom of the letter. Double check the overview and the summary to make sure it still supports the body of the letter.
If submitting a petition with several signatures, it's important to solicit input from everyone who signed it and include some of their points in the letter.
According to the Copyblogger Web Marketers' web site, persuasive writing is "generally an exercise in creating a win-win situation. You present a case that others find beneficial to agree with. You make them an offer they can't refuse, but not in the manipulative Godfather sense."
Copyblogger offers 10 key ideas for persuasive writing: Repetition, Reasons Why, Consistency, Social Proof, Comparisons, Agitate and Solve, Prognosticate, Go Tribal, Address Objections, Storytelling.