I'm pretty much paraphrasing some of the things you've noticed actually, but here goes.

I mainly pay attention when I'm out of a hand, because I'm quite conscious of giving things away myself when in a hand. Swallowing after making a bet and little hand shakes as a player sizes up their chips seem to be things I notice a lot. Chip stacking/tricks are also something worth paying attention to, some people are constantly playing with their chips and will suddenly stop, which can be indicative of either strength or weakness on their part.

One thing you've missed is how the other player actually puts their chips into the pot. Verbal snap call, the assertive 'all in' where their entire stack is either nonchalantly pushed over the line or picked up and placed over the line with some force, whether they're visibly looking at the pot and sizing up their bet and stacking chips, that kind of thing.

When in a hand myself, and particularly when action is on me post-flop, I'm wary of giving anything away so I avoid direct eye contact and try to look consistently weak (or apathetic, I'd like to hope). For a raise I'll just announce it and throw a big chip in rather than sizing up the exact bet with individual chips - bit of a pain for the dealer, but I think they're aware of this kind of thing and will generally sort out the change from the pot and from players not in the hand.

The stare down bizarrely does seem to be a reasonably consistent give away towards not wanting a call though, although you do really want to learn your players before relying on this.

Do they re-check their cards? Good indication of whether the player has a drawing hand, although some players will use this the opposite way by doing the whole 'let me just check I have what I think I have' thing when they know they still have those pocket aces post-flop. I'm still surprised that so many live players re-check their cards so often - I don't see how difficult it can be to look at them first time and just remember "As Jd".. but then you still have the players who look at one card at a time as they're being dealt as well, so who knows.

I'm wary about relying too much on 'tells' because some of the better (and more aggressive players, both in terms of action and talking) seem very conscious of their body language and will use this to their advantage to get you to make the wrong decision. Like you say, not everybody gives a reaction but I find that those who are worth watching are the quiet guys sitting with headphones on not saying a word.

I managed to get away from a monster preflop the other day just because of a gulp/shake of the hands from a TAG player I know well UTG. He got pushed all in by the short stack, it got folded round to me and I ditched my Jacks. He promptly called and flipped over his aces. Without the read I'd have probably pushed myself and tried to isolate the short stack knowing his range, so it's definitely worth paying attention to this kind of thing, but only with certain players.

Interesting topic and would love to read more.

EDIT: One more thing, at lower stakes live it seems very easy to see when some people ahead of you are going to throw their cards away - some people are so blatant about it that they may as well be folding out of turn. It goes back to the whole re-checking of cards thing though I suppose... look once, put a chip or protector on your cards and let the hand play out.