Julie Dao asked me in the comments to last week's WiP Wednesday about my character bios. I thought I'd take some time to go over those a little more in-depth than I did in the comments.
My biggest resource for questions to ask about my characters is Noah Lukeman's The Plot Thickens: 8 Ways to Bring Fiction to Life. The first two chapters of his book cover dozens of questions to ask. Chapter 1 is all about the external. What do they sound like? How about cheekbones? Wais size? All sorts of stuff like that.
Chapter 2 focuses on the internal. He covers topics like conversational focus, sub-conscious programs, religion, spirituality, etc.
For any given character I go through most, if not all, of these questions. Until I lose steam. Which is why I can only do a couple of character bios at a time. I make it a goal to at least cover the physical description questions and the stuff about tone of voice, accent, etc.
Take, for example, my bio for Derek, the MC from Lodestar. I've got 4 or 5 pages on him. I answer most of the questions found in Lukeman's book. But then for side characters such as Grady or Evans, I only have a page covering the basics of background and physical description.
Since in Lodestar ethnic background is important I make sure I note that for each character, regardless of how in-depth their bio may or may not be.
I hope that this helps answer Julie's question a bit better. I'll probably do another post on bios sometime, too. We'll just have to see how it goes.