When trying to spot poker tells, it is important to figure out each player’s baseline behavior. You need to know how your opponents appear in “normal” situations and then look for deviations.
Perhaps the most obvious tell that amateurs display is becoming obviously attentive when they have a strong hand and obviously inattentive when they have a weak hand. When someone likes their hand, they tend to focus, paying attention to each player’s action, and generally sit up a bit more. When they don’t like their hand, they become unfocused, slouch in their chair, watch TV, or talk to someone else at the table.
To demonstrate this point, suppose you raise with Q-J from middle position and both players in the blinds call. The flop comes K-8-5. If both players are clearly uninterested in continuing in the pot, you should make a continuation bet that will frequently steal the pot. However, if one of your opponents perks up and is clearly interested, you should check behind, conceding the pot. There is no point in bluffing if you don’t expect your opponents to fold.
You can also make deductions about your opponent’s hand strength based on how quickly he is breathing. In general, people breathe faster when they have strong hands and slower when they have weak hands. This is because most people who think they are about to win a pile of money tend to get excited whereas those who are bluffing subconsciously want to appear as innocuous as possible, resulting in them to holding their breath and being still.
For example, if everyone folds to you in middle position and you have A-9, if the player to your left, who has already looked at his hand, is breathing abnormally heavily, you should fold because A-9 fares quite poorly against a range of premium hands.
When you start focusing on breathing tells, you will find that some players exhibit the exact opposite tendencies previously listed, breathing quickly when bluffing and slowly with premium hands. It is important that you figure out each specific player’s tendencies and adjust accordingly. Do not fall into the habit of thinking that everyone will display the same mannerisms.
As you further study poker tells, you will find that most tells are somewhat unreliable unless you have witnessed a player exhibit them a few times in previous similar situations. Tells are best used to sway marginal decisions one way or the other. In order to make a “sick read” and drastically deviate from normally sound strategy, you must know your opponent extremely well.
Do not fall into the trap of making a big call simply because you “think” your opponent is bluffing. That is a quick way to end up without a bankroll.