One basic tactic is to keep a careful eye on the cards that other players draw & discard. You can learn a lot about your opponents' possible hands by keeping an eye on the cards thsattaking up comey are collecting or avoiding, and you can modify your own strategy accordingly. If an opponent is routinely discarding high-value cards, for example, it can mean they are attempting to minimize the value of their hand before going out or are aiming for lower-point melds. Effectively controlling your own hand is another essential component of rummy strategy.
