Jaynes' has thought a lot more about this than anyone I've ever read. Another sign is that we think of consciousness as the thinking-about-doing-stuff part of ourselves. But, that can't be right either:
If consciousness is the mere impotent shadow of action, why is it more intense when action is most hesitant? And why are we least conscious when doing something more habitual? [pg. 11]
As I sit here and write, I'm conscious of the point I want to get across to you, and the words that might help me do it. But, I'm not conscious of how I type, or the fact that I'm wiggling my ankles a bit, or that my feet are a bit cold, or that I'm sitting a little off-center so that my left thigh hurts. I'm conscious of them now ... but I wasn't before. What was I conscious of then, and what was going on with that stuff I just listed that I wasn't conscious of?