Your people

You should really know your characters, well, before writing about them, you know. They are your best friends.

You know that you don't "create" your characters. They just appear, like any new acquaintance, and what's left for you is to learn to know them, observe them, interview them.
If you really care about your characters, you will remember Harry's eye color. If you don't, no-one else will either.

Unleash Your Characters
Creating Character Profiles