Card counting in Blackjack improves a player's odds by tracking the ratio of high to low cards remaining in the deck. Players assign values to different cards to maintain a mental tally, helping them determine when the deck is favorable. A high count—indicating more ten-value cards and Aces—encourages players to increase their bets, while a low count leads to smaller bets or sitting out. This strategy requires practice and discretion, but effectively adjusts betting based on the game's flow, ultimately enhancing the chances of winning against the house.