>It might be better to back-fill their childhood as those experiences become relevant to the plot.It might be better to back-fill their childhood as those experiences become relevant to the plot.
Yes, this. I do a lot of back-filling as I develop the story. I have a character, for example, who generally dislikes and mistrusts the nobility. I threw that on him like one throws on a new coat, just to see if it fit. It felt right after a while, seemed useful in story development, but then I had to ask *why* the character had that attitude. I found a historical event that seemed suited to the purpose and had a noble cause the death of someone the MC respected and admired. A classic case of noble privilege doing damage.
I'm still fuzzy on the details of exactly what happened, and how close to the event the MC was (did he witness it? hear about it?), but I tend to address such details as I need to in order to move the story forward. I should add that this doesn't necessarily mean as I'm writing the story. Sometimes such back-filling happens as I'm thinking and taking notes--sketching with words. Sometimes the details never even make it into the story, but they form the weave of what makes the character, so when I come to write a scene, it's there to inform the character's actions.
I think one reason why I never found character sheets, in all their various forms, to be helpful is because my process is so iterative. It's primarily a dialectic between plot and character, with setting and theme sometimes chiming in. Whether it's outlining the story or making a character dossier, doing all that up front never seems to survive even the first chapter or two of actual writing. That said, I recognize there are others who make detailed sketches of their characters.
If I were a playwright, I'd have characters come on stage and then everyone on stage would have to take a few moments deciding on the newcomer's name! I'd make a terrible playwright.