In addition to Tells, you might want to be alert to cheating, especially if you play live (i.e., not online) with strangers.
If a guy deals seconds, and he’s any good, you won’t see him doing it, but you damn well will hear it. In this form of sleight, the dealer keeps a card on the top of the deck and deals the one imediately below it. He does this to every guy in the game until he comes to his hand and then he deals that top card - usually an Ace or King to himself.
In 5-card and 7-card stud, and Texas Hold 'em, this is a huge advantage.
I encountered such a dealer only once, and he was so good, I was more fascinated by his skill rather than resentful at his chicanery.
Try the basic move yourself. Don’t make any attempt to be subtle about it. With the deck in your left hand, push the top card a little to the left and deal the ones below it, as if you were dealing a six handed game. You’ll find that in the process, the second cards cannot help but rub against the top and third cards so as it comes out of the deck you hear a swish. And as those card go to each player, you’ll hear swish, swish, swish in rapid succession.
It’s a marvelous Tell in itself with such a distinctive sound, that once you hear it, you’ll never forget it.
I cannot remember when or where this game occurred. It was a one time affair, and the second dealing is the only thing I can remember about it plus the fact that he looked and acted like an absolute straight shooter.
Dealing seconds requires some skill and lots of balls. To do it properly, you must push the top card aside, peel out the second card and move the top card back to it’s original position, very fast and very smoothly. And you have to do this for every player at the table except, of course, yourself.
And although I stared at that deck like my life depended on catching him visually, I couldn’t do it.
Of course, I urge you never to try cheating of any kind in a poker game. You risk getting hurt - or worse.