‘Tells’ are highly overrated, in the sense of spotting someone’s nervous tic or whatever. Physical tells are hard to spot, and not worth much, IMO.
It’s much more important to learn to spot playing strategy. What range of hands a player is likely to have in early position. Which hands a particular player is likely to hold if he raises. That sort of thing. Also, learn to watch a player’s chip stack, and know whether they are winning or losing. Players down a lot of money often go ‘on tilt’, and lose their composure (and their skills). They are likely to play looser, and to pay off bets with very little. Do not try to bluff someone who’s stuck a thousand dollars at three in the morning.
Players who are up a lot of money often play more aggressively. Players who WERE down a lot of money but have gotten back to even usually play very tight - they’re thinking, “Man, I’m lucky I got all my money back. Okay, now I’m going to settle down and play really solid poker. No more taking chances!” A player like this is likely to release a middling-good hand, and a bluff with a flush draw might be profitable.
There are also some ‘psychological’ tells. For example, if a flop comes up all diamonds, watch for the players who pick up their cards and look at them again. Chances are, they have two unsuited cards, and they are looking to see if one of them is the same suit as the three on the table. Most likely, they have at least one big card.
To give you an example of how a ‘read’ like this might work, let’s say a player calls from early position. I know him to be a solid, reasonably tight player. The flop comes up K94, all of diamonds. This player glances at his cards. Now, there is a very limited range of hands a tough player will call from in early position - either big suited cards (AJs, ATs, KQs, a couple of others), or a big pair, or very big unsuited cards (AQ, AK, KQ maybe).
Out of these unsuited hands, most players would raise with AK, AA, KK, QQ. So my guess at this point is that he’s got AQ offsuit, and he was checking to see if his Ace was the same suit as the diamonds - most players, if they have two suited cards, remember the suit. If they are offsuit, they aren’t playing for a flush, and may not pay attention to the suits. That’s why he had to check again. Also, if he doesn’t bet, he probably doesn’t have a king, because most players would bet a pair of Kings in this position. He might be going for a check-raise, so I’ll keep that in mind.
So now I’m tentatively putting him on AQ, maybe AJ or possibly AK. Of course, he could have something else - never tie yourself to a read in the face of other evidence. But I’m pretty sure he doesn’t have suited connectors, like 7s8s - lots of players will play those cards from early position, but a three-diamond flop wouldn’t have given him a reason to re-check his cards.
Now, let’s say I’ve got Qd9s. So I’ve flopped second pair, and a draw to the second-nut flush. First player checks, the next player checks to me, and I bet my second pair/flush draw. Player behind me calls, and the next player raises. The first player cold calls the raise. Now my suspicions are pretty solid - he’s drawing to the Ace of Diamonds, and my Queen of Diamonds is no good. Neither is my second pair with a raise and a call behind me. So when the action gets to me, I fold.
That’s the way tells get used in a real game. Not, “Oh, he’s scratching his ear, and he always does that when he has a big hand!”. That stuff is mostly for the movies. Real life is all about understanding behaviour.
Here’s another one of my favorites - Seven card stud, and a player has three diamonds showing. He bets, representing the flush. I fold and let him have the pot. He looks at his hold cards one more time before throwing them away. What does that tell me? It tells me he probably had the flush. It’s a ‘pretty hand’, and players like to look at pretty hands. If he was bluffing, why would he want to look at his busted straight or whatever? Who cares? So that little tell gives me some information about this players betting and bluffing habits that less observant players won’t pick up on.