One of the most important things you can do at the table is distinguish between the
good players and the weak players. To take this further, you should distinguish
between tight/loose and aggressive/conservative.
When a tight player enters the pot preflop, you should call less often, especially if
they have raised. On the other hand, you can play more hands against loose
opponents. For example, if a loose player raises in early position, I might be more
inclined to play AQ than I would against a tight player- When your opponents play
poorly after the flop, you can also play more hands since they will pay you off more
when you hit a good hand.
After the flop, be very selective when you try to bluff loose players. They tend to call
a lot even with weak hands, so it is difficult to get them to fold a hand. If they are
also aggressive, you can try to induce bluffs from them since they are always trying
to bet and win the pot. On the other hand, tight players will fold their weak hands
and sometimes even top pair with a weak kicker, so bluffs and semi-bluffs have a
better chance of success. Inducing calls is also a good strategy against tight
opponents since they will probably fold to a bet with any kind of weak hand.