i make the facial expressions that i'm drawing and sometimes i laugh by myself thinking of what the character might be thinking while i'm drawing him/her or the scene that could happen after/before the scene i draw has happen 0_0
I blur my vision a lot. Like starting to but not quite crossing your eyes, y'know? If whatever I'm working on is in my lap, I also have a tendency to slowly lean over so I eventually end up nearly curled in a ball and giving it the Kubrick stare. I'm trying to break that one before it breaks my back.
I do the same as you. I also have a tendency to tilt my head a lot, never really thought about why I do it though. I also lean back, probably for the same reason as squinting. Other than that nothing comes to mind. A friend of mine does this thing where he sucks in air when he draws, as if he's taking the first sip from an invisible pint.