"I put you on ace-king!"
Possibly the most overused phrase in poker, this generally comes out of the mouth of the preflop pacifist who just got all-in with some measly pair on a flop that didn't include an ace or king. I heard this statement recently, rolled my eyes and wrote this down.
The ability to put an opponent on a precise hand is nearly impossible. There are many possible hands and limited information, and poker is played by moody humans.
What we can do is always consider the range of possible hands held by our opponents. All the information we have should factor into our ranging. When we have an ace in our hand, it makes it 50 percent less likely for our opponents to have pocket aces, and 25 percent less likely for them to have a hand containing an ace.
Accurately defining ranges depends on long-term information-gathering. Seeing hands at showdown is gold. If we can deduce that Opponent A is raising the top 10 percent of his hands and limping the next-best 10 percent (a common trend in live poker), then the second he puts money in the pot, we've eliminated 90 percent of the possible holdings for that opponent. If the opponent instead raises the top 20 percent of his hands but never limps, we've narrowed his range, but it's going to be more difficult to deduce exact hands because the number of possible starting hands is doubled.
Let's evaluate a hand vs. Opponent A.
Action folds to him in middle position,
The flop comes Ah 10c 5d. We check, he checks.
What does this mean? First, we can probably eliminate the top end of his range, but not always, because sometimes people are deceptive. We can also probably eliminate his garbage, since garbage would usually bluff this flop, but there isn't much garbage in his preflop range. Moving into the turn, we should narrow our range on him to: K-K, Q-Q, J-J, 9-9, 8-8, K-Q, K-J, Q-J, Q-10, A-K, A-Q, A-J, A-9. We'll also see the occasional A-A, 10-10, or A-10 from players trying to get cute with their monsters.
The turn is a Qs, a very good card for our opponent's range. We check, and our opponent checks. This likely means that our opponent has some sort of hand that doesn't need to bluff but does not want to play a big pot. That narrows his range to K-K, J-J, 9-9, 8-8, K-Q, Q-J, A-K, A-J or A9. We can easily quantify our equity with A-J vs. that range. (It's 68.97 percent, according to PokerStove.com.)
The river is a 2h. We should bet, because considering our opponent's range of hands, they all contain showdown value, but many of those hands are more likely to call a bet thinking we're bluffing rather than bet themselves for value. Since there are no hands in our opponent's range without showdown value, it means our opponent is not going to bluff, giving us no reason to check to try to let him bluff.
It's easy to narrow the ranges of weak opponents and get a general idea of what their hand is. You just need to pay attention and do some reconnaissance work. If your play is such that your opponents can figure out what you have, then you're doing it wrong. Sprinkle in some nefariousness and make some raises with less-than-powerful hands.
Bryan Devonshire is a professional poker player from Las Vegas. Known as "Devo" on the tournament circuit, he has amassed more than $1 million in career earnings.