You can learn something about the possible melds they are attempting to complete by keeping an eye on the cards they choose. With this information at your disposal, you can decide which cards to discard & whirummy all apch to hold onto in order to keep them from completing their melds. Taking into account the potential value of each card in your hand is another method for determining when to discard & when to keep cards. You can strategically decide which cards to discard to stop your opponents from completing their melds and which to hold onto to complete high-value sets and runs by assessing the potential value of each card.
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