Prepare an overview of the project. The overview is commonly at least 10 pages long and should include as much information about the project and you as possible. Include information about the reason for writing the book and the experience and knowledge you bring to the project. The overview can include references to similar works but should also include why your project will stand out.
Write at least the first two chapters of the book. Include an extra chapter if the chapters are short or if the concept is complex and doesn't become evident in the first chapters.
Prepare the table of contents for the book. This helps define the book and shows the continuation of the concepts of the first chapters.
Prepare the author's biography. Include any education background or practical experiences applicable to the book idea or concept. Also include practical experience that you have that might aid in book promotion such as experience working with the media or on the speaking circuit. Package the bio with examples of previous works and publications.
Write a cover letter. Research the publisher and address the letter to the appropriate editor for the type of work you are pitching.
Package the entire content, along with an envelope with prepaid postage, and mail the proposal to the publisher.