Understanding which cards have been played can give important information about the probability of drawing particular cards, even though it might not be as complicated as card counting inrummy sites games like blackjack. A system for keeping track of which cards are discarded and which are still in play should be developed by the players. You can accomplish this by mentally recording the ranks and suits of the cards that have been revealed throughout the game. Players can choose which cards to draw or discard more intelligently if they keep track of these details.