First, if you have a pocket pair, this is where most people can make some crucial mistakes. It's definitely bad to 4bet 22-77. If
you've gotten into a situation where 4bet > call > fold, then
you've done something wrong. You can probably avoid this situation if
you minraise them preflop instead. If you have 88+, it's never bad to 4-bet your opponent.
Calling 3bets with hands like KJ or JT are some of the biggest mistakes I see people make in HUSNGs. Probably just fold suited connectors as well unless you're very, very deep.
If your strategy isn't working, and your opponent is 3betting you OOP with
air a lot, you need to consider a new strategy. Raise fewer hands
preflop, so your range is stronger on average when you are 3bet.
Remember that being the recipient of a 3-bet is a double edged sword. First, it's bad because it forces you to a decision to play for stacks. But, it's good because your opponent has put a large chunk of stack on the line out of position. You need to learn to pick up on the opportunities that this gives you, either by taking it away from him now or by folding your mediocre hands to encourage him to continue to make this mistake against you.
