You should, of course, exercise caution when there are four cards of one suit on the board and you don’t have a flush. But sometimes you should bet right into that board without a flush.
The best time to bet is when you have two pair, three-of-a-kind, or a straight against a lone sophisticated player who has checked into you. If there were raises before the flop and parts of the four-flush on the board are high cards, especially an ace, figure it’s more likely that your opponent does not have a flush.
He is more apt than usual to hold high cards, and those high cards are likely to match the suited cards on the board. There are fewer likely ranks that will provide your opponent with a flush, and it’s more likely than usual that he has a pair. So, sometimes bet two pair. Not only can this be a profitable decision, the play will enhance your image. — MC