Don’t be too sure about that! https://xkcd.com/610/
That said, (based on my own experience anyway) I think you’re right that there are times of life when we are more conscious and less so. It’s a spectrum, not a binary thing.
Finally, there’s Chalmers’s idea of “philosophical zombies,” which would appear conscious according to all the criteria you give, but have no actual interior consciousness at all. (Opinions differ on whether this is a meaningful concept.)
This is only true for the outward behavior we define as consciousness. The experiential part of it (qualia and such) can not be described in objective terms (try describing 'redness' by itself). That is the hard problem of consciousness.
What you can do in that realm is experiment with n=1 using optical illusions, psychedelics and dissociatives (in ascending order of how weird you want things to get).
Philosophically: You can being building criteria for consciousness; the things you look at in yourself that tell you are, and then begin looking for that (or symptoms of that) in other people.
Anecdotally: you can totes spot "unconscious" people. You can even watch people gain consciousness, if you watch 'em in the right circumstances. You can even watch yourself regain consciousness (for me it's usually a sensation of "what was I even doing for the past day/week/month).
All of this gets at least as weird and fuzzy as trying to define "consciousness" in the first place.