Think honestly about your experiences, too. Don't just focus on the best parts of your memories; think about the details within those times. While Christmas morning may be a magical memory, you might also consider the scene around you. Include details like your mother making breakfast, your father spilling his coffee, someone upset over relatives coming into town, and other small details like that. Understanding the full experience of positives and negatives helps you paint a better picture for the reader and lead to a stronger and more interesting narrative. Learn to tie together all the interesting elements of your life story and craft them into an engaging essay.
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.