Gather all available records, materials and writings by or about your subject. Even if you know or knew the person intimately, you must gather a wealth of knowledge and factual information to add detail and color to the biography. Contact the person or his estate to get permission to access personal papers like journals, letters, diaries and writings that can reveal past activities, feelings or opinions.
Read all the material, compiling notes and ideas for things to include in the biography. As you research, consider ways to break up the material into phases or sections, to give the book shape. Cliche biography sections are life stages like "Childhood," "Adolescence" and "Adulthood," so try to create unique or more personal divisions for the person's life that truly show how he was shaped or changed through life.
Interview living relatives, close friends or business associates of your subject. Interviews can provide intimate portraits and different perspectives on the person's life, accomplishments and opinions.
Construct a rough outline of the biography as a whole, detailing sections, chapters or other divisions. For each section, include relevant major happenings, ideas or events that will shape the book for you and aid you in your writing. Include quotations, notes and citations to references in sections for facts, dialogue or other important information to aid in your citations.
Write the introduction or preface to the work, in which you detail the major aspects of the book. Give a miniature biography or snapshot of your subject's life to pull readers into the book. An introduction or preface also helps you get a better grasp of your vision of the book.