You will learn important information about which cards they are keeping and which ones they are throwing away if you do this. You can use this information to identify important card combinations that they might be attempting to complete as100 spin well as to predict possible sets and sequences. You can modify your approach and choose which cards to pick and discard sensibly if you keep track of this information. Following your opponents' movements by observing how they respond when they select or discard particular cards is another useful tactic. When an opponent picks a certain card, their expressions of excitement or disappointment can reveal important information about their hand and possible sets and sequences.
