I've mentioned before I don't write a full character biography before a story but I do love to work from that character's central trait as that then tells me how they are likely to behave in most situations. I find it easier to flesh out other details from that point.
But whatever way a writer chooses to create their characters, perhaps a review of them every so often is something worth considering. Why?
- To check the characters are still coming across the way you want them to do so.
- If they're not, is this because the characters have developed?
- If so, is that in the way you wanted them to develop or is it something that has come out of your initial story ideas? The latter is no bad thing but it pays to check you are happy with this. What should happen is your character is now stronger than they might otherwise have been.
- If they're not, why is this? Is it something you need to fix or is the character meant to become weaker? Do you need to go back in and rewrite the story as a result of these changes or do you need to rethink the character?
- To check the character is still playing a vital role in your story. That vital role can be a small "walk on part" if you like but it still has to be crucial. If not it and the character should be cut.