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WHEN TO FOLD AND WHEN TO RAISE
We have said, up to this point, that the two main defenses against the semi-bluff are simply giving up and folding, or raising. (In all aces cases we are assuming the pot is relatively small.)
The question now is when to do the one and when to do the other. That is, when do you fold, and when do you raise?
Obviously when you have a very poor hand, you fold. When you have a big hand, you raise unless it’s so big you want to slowplay and trap your opponent later. The difficult decisions occur when you have a medium- value hand. There are three principle criteria you should use in deciding whether to raise or fold:
1. The chances your opponent is bluffing or semi-bluffing.
2. The chances that opponent will outdraw you if he is betting with the worst hand.
3. The chances you will outdraw that opponent if he is betting the best hand.
The more you believe your opponent id bluffing or semi-bluffing, and the greater your chances of outdrawing him if he does have a legitimate hand, the more you will tend to raise.
On the other hand, the smaller these chances are and the greater the chances your opponent will outdraw you if he is poker betting the worst hand, the more you would tend to fold.
Recall an example earlier in this chapter. The chances that your opponent had the best hand were quite high (48 percent) the chances of your outdrawing him were so low as to be virtually nonexistent.
At the same time the chances of your opponent outdrawing you were very high (you were only a 6-to-5 favorite if he didn’t already have you beat). It was the combination of all these chances that dictated a fold.
EXCEPTIONS WHEN CALLING IS CORRECT
We have said that either folding or raising is the correct play against a possible semi-bluff most of the time. There are three situations which just calling would be correct.
Calling a Possible Semi-Bluff When the Pot is Large
First, you would call when the pot is large, even if there’s a chance you opponent is semi-bluffing. Possessing any kind of competitive hand yourself, you certainly don’t want to give away a big pot to a possible semi-bluff.
So you can’t fold. At the same time, there is no point in risking a raise since, because of the size of the pot, your opponent will call even if he is semi-bluffing. And if he’s not semi-bluffing but has the best hand, he may reraise you. Therefore, the only play is to call.
Calling a Possible Bet On the Come
Secondly, in stud and holdem games, it is usually a mistake to raise with a good but not a great hand when you think your opponent particularly a very tough opponent has bet or raised on the come for a flush or a straight.
If his bet was legitimate, he probably has you beat, so you’re simply donating money to the pot. If he was on the come, he has an easy call of your raise, which eliminates most of the reasons for you to make it.
Thus, even if you were quite sure that the Q 
J 9 earlier in this chapter had only a four-flush, you would not be correct in raising. You would only call.
However, when you call an opponent who you think is on the come, you usually do so with the intention of betting right out on the next round any time that opponent draws a blank card that would not make his hand if he was in fact on the come. You now become the favorite if your opponent was on the come, and you don’t want to give him a free card.
There is a mathematical reason for you to play your hand this way. Let’s say you bet with two cards to come, and someone raises you.
You estimate that there is a one-third chance that player has you beat and a two-thirds chances he is on a draw. Nevertheless in most case he is still a mathematical favorite.
So you can only call the raise since you’re the underdog. However, when the next card cannot have made his flush or straight if he was drawing to it, now, with only one card to come, you have reverted to being the favorite.
So you should usually bet. One the other hand, if that card makes the possible flush or straight, you should usually check and fold if your opponent bets, unless you are getting good enough pot odds to chase.
Your opponent almost certainly has you beat, whether he was originally betting a legitimate hand or betting on the come.
Here is an example of this calling defense against a possible semi-bluff that come up when I was playing recently in a seven-stud game.
I started with a three-flush and a 10 showing and was lucky enough to make three 8s on fifth street. I bet, and a good player who caught a K 
with the J as his door card raised.
I reasoned the raise meant one of three things. Either my opponent had started with kings in the hole, in which case he was raising with the best hand; or he had started with two jacks, made a flush or a straight draw.
I called the raise. When no heart, ace, or 9 fell on sixth street, which might make a straight or flush, I bet right out, much to my opponent’s surprise, for my opponent had been expecting to get a free card.
It turned out the opponent was in fact on a flush draw with a small pair, and the three 8s held up. (Of course, if a heart, ace, or 9 had fallen, the play in this instance would have been to check and call since there was a reasonable chance for me to make a full house on the last card.)