The most effective card counting systems in blackjack vary in complexity and effectiveness. The Hi-Lo system is the most widely used and accessible, as it assigns simple values to cards, with low cards (+1) favoring the player and high cards (-1) favoring the dealer. KO (Knock-Out) is another unbalanced system similar to Hi-Lo but easier to use since it doesn’t require converting the running count into a true count. More advanced systems, like the Zen Count and Omega II, provide higher accuracy by assigning different point values to cards, but they require more skill and practice. The Red 7 system is a middle ground, offering a balance between simplicity and effectiveness. Finally, the Wong Halves system is highly precise, using half-point increments for greater accuracy, but it is also the most complex and difficult to master. In general, simpler systems are easier for beginners, while more advanced systems can provide a larger edge if used correctly. However, all card counting strategies require significant practice, and casinos actively monitor players for such techniques.