Every novel and most nonfiction books other than textbooks have characters. Developing characters is a very important consideration for any writer.
Some writers may protest that a nonfiction book like memoirs are about real people, not characters. A character is the person or thing the book is centered around whether that entity is real or imagined.
In a memoir a writer may be writing a personal story, but that story happened in the past or is based on the past. And the person you were then is not the person you are now. So you must try to become the person you were then in order to write that story.
Your past self becomes a character.
For me developing characters begins with a general idea of my characters. What they might look like. A few character traits are added.
I read a book called “One Great Way To Write Short Stories” which had a list of possible character traits. I added a few I thought of. Picking a few off this list is a good starting point. It does only work for people.
Animal characters requires a knowledge of the animal and choosing character traits true to that animal. At one time animal stories were actually people stories with animals as the people, but that is no longer how most are done. When I wrote “Capri Capers”, the goats and kids were based on my own goats and experiences with them.
Developing characters then becomes putting the characters in a situation and writing the situation out. I write the situation letting the characters react to it using their basic traits. Those few traits morph and flesh out as I write.
National Novel Writing Month and Camp are good ways for me to do this. Since I can’t stop and edit without losing my word count, I push myself through. By the end of the story arc my developing characters are real characters.
Since I now have a clearer view of my characters, rewriting the novel lets me adjust the characters earlier in the story. This in turn adds depth to the story, maybe even changing parts of it to make the characters more real for the reader.