The characters have their own lives and their own logic, and you have to act accordingly." ~Isaac Bashevis Singer
Character is the heart of your memoir. Without compelling characters, you have no story. Readers like interesting plotlines, but if you don’t have a great, well-rounded character to place inside of your plot, the reader will put down the book. The reader has to care about someone in your memoir enough to follow him or her through the story. Make the reader root for your character.
A character should never be predictable, but you should know your character well enough to know what he or she would do in any given situation. In many memoirs, the main character is the writer, so you’re already ahead!
The most profound thing you can write about is not worth it if your characters aren’t interesting. Make your characters interesting through detail and desire. If the reader can see, hear, and feel the character, then you’ve made him/her real. If the reader can relate to your character’s wants and desires, then you have created a character worth following until the end of the story. A character that wants nothing is worthless to your story. Since you are writing memoir, you have to choose the part of your story where the character’s desire is overwhelming.
A writer begins by breathing life into his characters. But if you are very lucky, they can breathe life into you." ~Caryl Phillips
Gesture and action reveal character far better than any thing you could ever tell the reader about your character. Make your characters active, and we'll understand them—simply telling us a character is good, bad, afraid, etc. is not powerful. Tim O'Brien does this beautifully, story after story, in his collection called The Things They Carried. The title story in this book focuses on the things that a group of soldiers carry with them through Vietnam. The reader learns about the characters through the details of what each individual man carries—it's a gorgeous story.
Begin with an individual, and before you know it you find you have created a type; begin with a type, and you find you have created—nothing." ~F. Scott Fitzgerald
Last, but certainly not least, crisis reveals character. This is something that you must have certainly noticed in your own life. When there's a crisis, everyone's true nature suddenly springs to the surface. The person that you thought was a rock suddenly runs like a gazelle away from the problem, while someone you thought of as a mere acquaintance comes though for you. It's the same for your characters. Since you know that a story is made up of conflict and crisis, and you will dutifully include as much of it as the story warrants, the reader will naturally see how the character reacts, and that reaction is better at revealing character than any 1000 pages of telling us about him could be. Action and reaction do more for your story than telling ever could.