Here's another one I keep getting asked about, so I'm going to break this down as simple as it can get with a chunk of something I've written up for a coaching session later. When facing a 3-bet, your opponents will have one of three characteristics, and the first one of those characteristics will never happen, so you've only got to deal with the last two. Here are the three possible characteristics:

1. They play optimally and you can never get an edge no matter how you play.
2. They fold too much.
3. They don't fold enough.


The adjustment for #2 is that you 3-bet bluff more and/or 3-bet for value less.
The adjustment for #3 is that you 3-bet bluff less and/or 3-bet for value more.

Here's an example for #2. Villain is 14/12 with a 30% attempt to steal. Villain opens for 4x in the button, and we 3-bet to 12x in the SB with 72o. We're betting 11.5bb to win 5.5bb, so if Villain folds more than 11.5/(5.5+11.5) = 67.6% of the time then we immediately profit as long as we aren't -EV post-flop (which we can always prevent theoretically by always check/folding post-flop). So Villain has to be continuing with more than 32.4% of his opening range, which is around 10% of all hands. To give you an idea of how unlikely this would be, the range {77+, AJo+, ATs+, KJo+, KJs+} is exactly 10% of starting hands.

Here's an example for #3. Villain is a 14/12 who opens UTG with {AQ+, 66+}, and will continue to a 3-bet with {AQ+, 99+}. A 3-bet bluff is no longer going to be profitable by itself, but we can open up our value range a bit with hands that perform well against {AQ+, 99+}. Our 3-betting range becomes something like {AK, JJ+}.

At our full ring games, scenario #2 happens a LOT more than scenario #3.
In our 6-max games, scenario #3 tends to happen a LOT more than scenario #2.