What's your central conflict? What's the biggest obstacle life presented that took years to overcome or come to terms with? Maybe it's an illness you were diagnosed with at an early age, a relationship wrought with turmoil, a series of career setbacks, a goal you worked for decades to achieve, or any other number of things. Look to your favorite books and movies for more examples of conflicts.
According to the fascinating field of “narrative psychology,” the stories we tell about ourselves are the key to our well-being. If you’ve interpreted the events of your life to mean that you’re unlucky or unwise, it’s hard to look optimistically at the future. Conversely, if you acknowledge that you’ve made mistakes and faced difficulties but seek (or have already glimpsed) redemption, you’ll feel a much greater sense of agency over your life.
Be revealing. You don't have to be explicit, but it's important to reveal truths about yourself and your life in an autobiography. Don't let the book become a list of your accomplishments, with all the negative material carefully kept under the rug. Present yourself as a whole person, sharing talents and flaws alike, and your readers will be able to identify with you and hopefully root for you as they make their way through your story.
Develop a central theme, main idea or thesis that clearly explains the purpose behind your autobiography. For example, your theme might be about how you overcame obstacles to become a stronger person, or it might explain why a particular passion -- such as mountain climbing or rescuing animals -- is so important to you. Back your theme with details and background information about your life experiences. For example, you might explain that your dad is in the military, so you've had to learn how to adapt quickly to new schools and unfamiliar environments. Or, you might discuss what it was like growing up in a poor, single-parent home, but how your family was always willing to take in injured or stray pets.