It's one of the first things you learn when playing tournament poker: don’t bet into a dry side pot. That is, if you and an opponent see the flop with a third player all-in, you should not bet unless you hold an extremely strong hand, because it’s more important to eliminate the all-in player than win a few extra chips.

This has become one of the most common fallacies in poker today. There are many situations where it is clearly correct to bet rather than attempt to knock out the third player, even if there is no side pot. But even some successful tournament players do not know about them, and may even brashly criticise you if you make such a ‘mistake’.