Reading your opponent’s hand, especially in middle to late stages of play, is a matter of skill which you need to build up over time. The beginner has virtually no conception at any time of his opponent’s holdings. The good player has a reasonable idea, but cannot eliminate certain cards. By the eighth card played, the expert player has a pretty fair knowledge of what the opponent is holding in his hand. By the sixteenth card, the expert player can practically read the hand card for card and has almost always determined his opponent’s exact hand. This is the point in which you want to get to.
There are various clues and bits of information that help you to read your opponent’s hand, such as his discards, his picks from your discards, your own hand, and his playing rhythm. His discards generally tell you what he does not want as far as the cards are concerned. You will know that when playing against a high knock that if your opponent throws an Ace or two, he does not need low cards for a knock, but he is trying to complete a meld. The reverse is also true if he picks a low discard, and throws a high one, you know he most likely already has six cards melded and is after cards that are low enough to enable him to meld.
By considering your opponent’s discard, together with what you are holding in your hand, you can obtain considerable information. For example, if your opponent discards a 9♣ he is not holding a meld of 9’s. Therefore if you are holding the 8♥ and 10♥, it would be to your benefit to hold onto them as long as possible. You also can figure if he picks the 9♣, and discards the 9♠ he already has a club sequence and could easily have the 10♣ tied up. If you are holding a pair of 10’s then you will realize that your chances of obtaining a third 10 will be reduced by at least half.
When you are making a discard you should always try to have some control over the card by knowing what it can be used for in case your opponent picks up the card. If you do not know what it can be used for then you are at a terrible disadvantage in the various cards you will be forced to hold. You will of course know certain cards that your opponent is not holding, because they are in your hand. The knowledge of these cards plus the cards that are already been discarded will help to eliminate certain melding possibilities which will help you to determine the melds or possible melds that remain available to your opponent.
This is especially helpful when you are trying to spot a salesman. The first step in determining if they are throwing a salesman is to figure out what kind of player you are playing. You need to know if they are extremely aggressive, mildly aggressive, middle of the road, mildly defensive, or extremely defensive. If you can figure this out, and you know the cards that have been discarded, and the cards that have been picked up, then you will know immediately if they are throwing a salesman.
It is incredibly important to build your skill to the point where you can do this, and not make any mistakes.