The semi-bluff is defined as a bet with a hand likely to be behind when the bet was made, but with good prospects to improve to the best hand at later rounds.
The semi-bluff can be played as a bet, a raise or even a check-raise. It is a sophisticated move more appropriate to mid or higher stakes. But be careful not to overuse it at the micro-limits or small stakes, as straightforward play is all it takes to be a winning player there, while fancy play is more likely to backfire.
How to semi-bluff
The typical hands to semi-bluff are open-ended straight draws and flush draws. By betting these cards, you can win the hand immediately if your opponent folds, or you can also win later if you hit your draw. Semi-bluffs work better if you are heads-up against one player, as it is much harder to make two or more players all fold, because they may like the prospect of winning a big pot.
Semi-bluffs work best in tight games, where cautious players tend to fold to raises. Or near the bubble in a tournament, when players play the tightest. They will not work against an opponent who cannot fold, like in many low limit ring games or small buy-in tournaments. Do not make this move if you are sure to be called.
In no-limit Texas Holdem, make sure that your bet size does not betray that you are making a semi-bluff. You should check-raise by the same amount either with your strong made hands or your semi-bluffs, for instance the standard three times the bet size.
Note that experienced players will see through the standard semi-bluffs if the board contains a flush or straight draw. Still continue to make such moves, but do not expect to win the jackpot each time. But the most deceptive types of semi-bluffs are the ones with double gut-shot straight draws or a gut-shot straight draw combined with a back door flush draw, as your opponent will not put you on such hands.
Another twist to make this technique even more potent is to check-call the flop, and then to check-raise the turn (independently of hitting your draw or not). As this move represents a very strong hand.
Advantages of the semi bluff
One of the main advantages of the semi-bluff is to make your opponents play incorrectly. According to the Fundamental Theorem of Poker, any time your opponent does not play as if he saw your cards, you gain and he loses. If your opponent could see your hand and assuming that you have the weaker hand, he should raise.
But most of the time he will call or fold, because he is concerned that you may have a strong hand, as you just bet, raised or check-raised. If he folds, this is the worse action, reinforcing your gain. Even if you do have the stronger hand, it is still correct to bet in order to avoid giving free cards to a weak hand.
Another advantage is that the semi-bluff adds a zest of deception and aggression to your game, making you less predictable than a straightforward transparent player who only check-raises with monsters. The aggressive style is believed to be the winning style, be it tight or lose, so semi-bluffing is an opportunity to take the initiative, and you should not pass on that.
It is also part of mixing up your game, as you can either open-bet or check-raise with the same semi-bluff hand, introducing confusion in your opponents who will keep on guessing. You should have different ways to play such semi-bluffs with straight or flush draw, and not always follow the same pattern such as always check-raising with the nuts flush draw.
In conclusion, the semi-bluffing technique is a weapon that you must add to your game and practice once you play beyond the small stakes tables. This is a very powerful method, easier to deploy and with better expected value than a pure bluff. You can train yourself at the lowest limit only if you use it with parsimony.