The introduction section is the shortest. Start out with a Cover Letter and a Title Page. Keep the Cover Letter brief: simply write a personal introduction to explain who you are and provide your contact information. The Title Page should be exactly what it sounds like: a title that introduces your proposal and provides a clear message about the ideas and/or services you are pitching. Some examples might be "Proposal to Create a New Executive Assistant Position", "Proposed Temporary Services to Benefit the Stuart Corporation", "Executive Search Services Proposed for Jameson Company", or "Suggested Candidates for the Vice President Position".
If you work in a Human Resources/Personnel department at a large corporation, or work for a small agency that sells temporary labor or executive search services, then you're in the business of evaluating personnel needs and pitching people and their skills. You may need to convince your boss or a new client of the need to create one or more new job positions, or persuade the boss or client to fill existing positions with personnel you recommend. Perhaps you are persuasive enough to do that with a phone call or casual conversation in the hallway, but odds are better that you will need to write a proposal to pitch your ideas and persuade the client or upper management.