A tactic that is frequently used in blackjack and other similar games, card counting can also be useful in 51 Rummy. Knowing which cards have been played can give you ione to appmportant information about what is left in the deck, even though it might not be as simple as counting cards in games where the objective is to reach a certain total. Players can decide which cards to keep and which to discard more intelligently if they keep track of which cards have been discarded and which opponents have picked up.