What is the name or description of the product, business service, or political issue that you are trying to persuade your readers to accept?
What negative points could your readers find in your proposal? Can you agree there is a downside, but persuade them it is minimal in face of the many benefits they will gain?
What specific action should the readers take if they accept what you are persuading them to do? When and how should they do it? Is there a deadline?
What details, specifications, features, or limitations of your proposed product, business service, or political issue would your readers immediately question? Provide that information in your persuasion letter.
What are your credentials or past successes and accomplishments? What facts can you produce to persuade your readers that you yourself are knowledgeable, trustworthy, and reliable?
What statistics, testimonials, documented evidence, or other evidence do you have to persuade your readers that what you are promoting is essential and invaluable, and promises to be of worth to them?
Selling something? Offer one of these incentives in your persuasion letter: