To keep opponents guessing, you must actively work to form sets & sequences while also thinking about how to move your hand. Holding onto high-value cards, for instance, can be advantageous if you believe your opponents areholy rummy about to win, but it can also backfire if you keep them for an extended period of time without creating any winning combinations. Players who want to play defense need to be careful about which cards they discard and how doing so could help their opponents. It might be prudent to refrain from discarding cards that could aid your opponent in finishing their hand, for example, if you observe them routinely taking cards from the discard pile.