The best way to track the deck in blackjack is through card counting, particularly the Hi-Lo system. In this method, you assign values to cards—+1 for low cards (2-6), -1 for high cards (10, J, Q, K, A), and 0 for 7-9. By keeping a running count, you can determine when the deck favors the player (high cards remaining) or the dealer (low cards remaining). To refine this, you adjust for the number of decks left, known as the "true count." While effective, card counting requires practice and concentration and can lead to being noticed by casinos.