In casino blackjack, high cards—tens and aces—are favorable to you, the player, and low cards—2s through 7s—are favorable to the dealer. With more tens and aces in the deck, more blackjacks will be dealt, and even though these Blackjacks will be evenly distributed between you and the dealer, you get paid 3 to 2 for your blackjack, while the dealer only gets 1 to 1—the amount of your original bet. In addition, more tens and aces mean that you will have more double-down wins and that the dealer will bust more often since the dealer must hit all hands of 16 or less, even when you are stiff.
So, all blackjack card-counting systems keep track of the high cards versus the low cards. When more low cards have already been dealt, leaving the deck(s) rich in high cards, this is favorable for you. When more tens and aces have already come out of the deck(s), the reverse is true. Most professional-level counting systems are balanced point-count systems. The counter assigns plus and minus point values (usually +1 or -1) to the various cards based on their value to him. The system is said to be “balanced” when there are an equal number of plus and minus point values so that the sum of all these values in a full deck adds up to zero.
As cards are dealt, the player adds the values of the cards he sees to his “running count.” The running count is the total count since the last shuffle. If you started your count at 0, then saw five low cards dealt (valued at +1 each), and three high cards dealt (valued at -1 each), your running count would be +2, since 5-3 = 2.
Once learned, this aspect of card counting becomes automatic and easy. The difficulty of playing a balanced point-count system comes when you must use the count to determine how much to bet and how to play your hand. First, the running count must be converted to a “true count” (there is an in-depth explanation of true count—for those who choose to use this more advanced technique—in a later section). Second, the player must memorize, and be able to apply, the correct playing decisions based on this true count. Learning to keep a running count is not difficult for most players. Applying the count properly at the tables, however, may be such a mental strain that many either give up on card counting completely or continue to count but extract very little value from their efforts. This is why simpler “unbalanced” systems were developed.