The direct mail is a pitch. I have used the following as a rubric to grade in-person pitches before. Perhaps this list will also help you in developing your letter:
• Is it clear who you are pitching to? Who is the decision maker?
• Are you clear on their need?
• What do they have interest in? What is their selling/sticking point?
• Who is their audience? Their clients? Who have they funded in the past?
• How can you align consumer trends to support your pitch story and align with who you are pitching?
• What demographics should you research? Use?
• Are you being creative? What is your style? What is your brand? How are you aligning to who you are pitching to?
• Have you turned up the heat? Made it immediate? Set a deadline?
• Remember it is all about the story – engage emotions. What story are you telling to sell?
• What do you want out of the deal? What are your requirements?