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First of all you should make for each character a short personal description - what they like, what they don't like, what problems they have, how they relate to each other, and so on. Just little t...
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#3: Attribution notice added
Source: https://writers.stackexchange.com/a/9144 License name: CC BY-SA 3.0 License URL: https://creativecommons.org/licenses/by-sa/3.0/
#2: Initial revision
First of all you should make for each character a short personal description - what they like, what they don't like, what problems they have, how they relate to each other, and so on. Just little things to give your character a defined personality. Some bullet points would be enough. Then write a short text only about the background story of your character. Write the things that will help you to remember the core content. That's enough because this way you'll have the possibility to embellish the story while writing. That's the way I do it and it helps a lot to define and save the personality of my characters which I want for them. You have a guideline but you are also not bound.