I have recently given a number of lectures for the Author Learning Center with advice for aspiring memoirists highlighting the emotions and the challenges involved with writing a memoir. I am also in the process of writing a guide to memoir titled More Than Words. First and foremost it's important to understand the difference between biography, autobiography, and memoir. Memoir is meant to be just a slice of your life, not the whole story. I recommend that aspiring memoirists begin by identifying your goals for writing your memoir - why do you want to write it? Understanding this will likely drive the theme of your story. Also ask yourself why readers will want to read your story. Before you write anything, be sure to understand your motivations and be ready to commit the time and discipline required.
Below you can watch the two-part, recorded webinar that I gave for the Author Learning Center on How to Write an Engaging Memoir.