Players can use card counting effectively in multi-deck games by tracking high and low cards through a value assignment system. They assign positive values to low cards and negative values to high cards, allowing them to keep a running total as cards are dealt. By adjusting their betting strategies based on this count, players can increase bets when the count is favorable, indicating better odds for winning hands. Maintaining focus and discreetly managing the counting process is crucial for appearing casual in gameplay. With dedication and practice, card counting can improve a player's chances in multi-deck settings, though it requires significant skill.