Do your characters tell you stuff you didn’t know
Until you started writing and found
To your idea they won’t be bound?
It’s for them to tell you, now show!
If your characters are strong enough, they will do the above, which makes sense given you’re giving them a fictional life. Let them live that fictional life to the full. You may find your story taking a different direction from what you originally thought but hopefully you’ll find it’s a better direction. I find I get my better ideas when I’ve had some time to think about what I’m working on.
Can you tell your characters apart?
Do you know what lies deep in their heart?
Their virtues and vices?
What they think a crisis
What makes them stop dead or make a start?
Quite proud of line 4 above - I don’t often produce slant rhymes where something sounds the same or similar but isn’t spelt that way.