When it comes to backstory, balance is key. Provide just enough to give context and depth to your characters without overwhelming the main plot. Sprinkle details throughout the story rather than dumping it all at once. Keep it relevant and engaging.
I try to include just enough backstory to give a character motivation for their actions in the present. Often that means I will have to circle back and add details when the story takes an unexpected turn. It's not enough that I know their reasons in my mind, the reader has to know them too. I will occasionally use flashbacks, but think it's better to set things up in advance. It brings about that "Oh, yeah" moment that captures the reader's attention.
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