Preflop, ranges can be pretty wide. I practice with pokerstove during my reviews so I can estimate what a 20/15 looks like vs. a 40/5.
After the flop is where I really start to narrow an opponents hand range. For example, If I hold A
on the button, I open, and the BB calls, I can put him on a wider range than usual since I'm in a stealing position. Any ace other than AK and AQ, any pair other than AA-JJ, suited connectors down to 56, unsuited down to JT, etc. (I'm assuming he would reraise AK-AJ, KQs, AA-JJ)
So lets say the flop comes A
The BB checks
I can't narrow his range. If I had some reads on his lead criteria, I might be able to deduce something.
You bet 3/4 pot, and he calls.
You probably have the best hand. He's calling with way worse in his range. You have all aces in his range beat other than AT and A2. You are ahead of KT, QT, and JT. However, this call only really narrows his range slightly.
The BB leads out with a pot bet.
Now things get tricky. What hands would he do this with? Lets say we check his stats and see his aggression freq. at 1.0. Odd play to lead out with that stat. KT would make this play, so would AT, A2, Axcc, QTcc, JTcc, TT, and 22. But let's say a few orbits ago, you remember the villain slowplayed his monster on a wet board (and he doesn't seem all that great of a player). With this the case, we can include a few of the best hands from his flop range as well. If we do the math...
AT, A2, KT, Axcc, QTcc, KJcc, JTcc, TT, 22 = 31 hands (27 that crush us)
Since he made a pot bet, how often do we have to be good here? Pot bet is 2:1 odds which means we have to be right 33%. In order for that to occur, 27 hands that don't have us crushed that we had bet against for value on the flop need to be included in his turn range. Is this reasonable? That's roughly 13 combos (we need 2:1 ratio of crushed hands to beat hands) or roughly 1.5 Ax hands. I think this is reasonable so I call.
River is a Q
and the BB leads for 1/2 pot
Bad card for you. Again, looking at the math
Axcc, JTcc, KJcc = 11 hands
KT, QT, AT, A2 = 30 hands
22, TT = 6 hands
Total: 47 hands.
How often do we have to be right? 1/2 pot bet gives us 3:1 odds so we need to be right 25%. Vs 47 hands that have us crushed, we need villain to make his play with 16 bad hands (or 2 Ax hands). Is he still going to play a weak ace in this way, with this board? Second pair with a good kicker? Maybe, and we only need him to play two weak ace hands to make this call, or one Ax hand and 12% bluffing freq. It's a marginal call in my mind. The question is, will he make the play with enough bad hands to make the call +ev?
Some of my hand combos may be double counted (I'm doing this at work), but this is roughly my thought process through a hand. As you can see, I only count hands that have me crushed that are in my opponents pf range, then figure out how often I need to be right, and then how many more hands I beat that need to be included in my opponents crush me range to make the call profitable. If he is more likely to over value some hands, this may make the play even more +ev. If I have some decent equity in the hand (draw to the nuts), and my opponent folds too much, I may reraise him as a semi bluff on the turn, and balance this at times when I have my opponents range crushed.