Choose a subject. Write about someone who interests you and who you feel could fill a book with life details.
Think of why the subject is special to you. If you can't write passionately about your person, you should probably choose someone else. Loving your writing topic will help readers love it as well.
Gather as much information as you can. It's better to have too much to work with than too little. If you know your subject personally, feel free to interview him and record the conversation or take notes. If your subject is a celebrity or historical figure, utilize encyclopedias and other credible books to collect details.
Organize your ideas before you start to write. Create an outline and zero in on highlights in your subject's life that you want to focus on. Details such as appearance, occupation and habits are a good way to make your biography more accessible.
Write your biography. Make sure you represent your subject accurately and appropriately. Use your outline and build upon each point. Tell interesting stories and avoid mundane tales that could happen to anyone.
Read your work out loud. You'll be able to pick out mistakes and spelling errors more easily if you hear them. You can also ask a friend or family member to read and edit your work, as it is simpler for an outsider to catch repeated information or flaws.