Your self-promotion letter could either be a cover letter with a resume, or an introductory letter offering your services. Self-employed consultants, for example, often write self-promotion letters as they are exploring new business opportunities. In lieu of a resume, the self-promotion letter must detail the consultant's expertise and value vis-à-vis the competition, and be clear, brief and direct.
Do not take any shortcuts on formalities, even if you know the letter recipients personally. This is a professional letter and your salutation and tone needs to reflect the professionalism that you bring to the situation, as well as demonstrate respect for the recipients. The salutation should be addressed to "Mr." for a gentleman; "Ms." for a woman, unless you know for a fact she routinely uses "Mrs."; or "Ladies and Gentlemen" for multiple recipients or if the names are unknown. Your closing salutation should be similarly professional, such as "Sincerely" or even "Respectfully Yours."
This first paragraph is your entrance to success, or to failure. It has to grab the reader and tell her to keep reading or she will miss something important. Do not just use this to talk about you, even though that seems contradictory to the point of a self-promoting letter. Instead, use it to align yourself with an important function of the company or to a need that you know the reader has. For example, if you have multicultural expertise and are proficient in several languages, you should identify with a company that is trying to gain market share overseas.
Who You Know
If you have a personal endorsement from an industry or community pillar that is significant to your reader, this is the time to mention it. You can take a humble approach that still highlights the magnitude of such a reference, such as, "I'm privileged to have worked with Ambassador Tom Smith for three years, and it is an honour to know that when he has training needs for his staff, I am the first person he calls."
Use your closing paragraph to ask for what you want, and to indicate your next steps. There is no sense in highlighting all of the great things you do if you are not specific about what you want. If you want a lunch appointment, state that. Also advise the reader that in consideration of her time and multiple tasks, you will be happy to follow up within a certain time period --- such as seven to 10 days --- to schedule a lunch or meeting.