Journals and diaries record thoughts, events and memories. Keep a journal if you plan on writing an autobiography or a memoir in the future. Be sure to note the date with every entry. Read your old journals when writing about your own life. Doing this will allow you to revisit your memories, remind you of past events and let you relive your feelings at the time. Use the journals of whomever you write a biography on if you have access to those records. You can ask the biography's subject personally to see his journals or ask his family members if he is no longer living. Be respectful and clearly articulate your purpose for asking. If you are writing a biography on a historical person, research to find out whether his journals have been published or are otherwise accessible.
Look at old letters and other forms of correspondence when writing about yourself and others. Letters like journals reveal your or others' feelings about events that have occurred in their lives. Letters also help to reveal past activities and participation in significant events. Review any old letters other people have sent you. They will likely contain comments and responses to letters you sent them describing your life at the time. Ask your friends and relatives if they have kept any letters you sent them. Ask your biography subject and her friends and relatives for old letters that will help develop a chronology of her life.
Do not lie in any autobiographical or biographical piece. The people involved in your altered true stories will know that you have fabricated information. They may publicly reveal your conceit, take legal action against you or otherwise threaten your writing career. If you want to incorporate over-the-top or fantastical elements into your writing, be sure to add a disclaimer either in body of the text or before the story begins.
Do not be purposefully libelous when writing a memoir, autobiography or biography. Do not write tell-alls about anyone but yourself. Revealing too much information that has the potential to malign your subjects risks complicating their lives or threatening their careers. It can also negatively impact the lives of your subjects' family members and friends. You can be honest in your writing without being libelous. Also, overtly libelous writing will come across as being gossipy and reduce your credibility.