What counters do is take advantage of the constantly changing odds in blackjack. In roulette or craps, the odds are mathematically fixed to be the same on every spin of the wheel or roll of the dice. In blackjack, the odds turn in favor of the player when an unusually large number of 10-value cards remain to be played. When the deck is rich in 10s, the player gets more blackjacks. So does the dealer, but players collect 3-2 on blackjacks while the dealer does not. In double-down situations, the percentage of the desirable 10-value cards for the player to hit is greater, and when the dealer's faceup card is a "stiff," or 2 through 6, it's even more likely than usual that the dealer will bust.
Counters make no attempt to keep track of every card in the deck. They simply track the concentration of 10s and aces. When the deck is favorable to the player, they increase their bets. When the deck is favorable to the dealer, they decrease their bets.
The counting is done with a plus-and-minus system. Players who feel they are ready to tackle blackjack on an expert level might want to seek out the more complex variations suggested in the many blackjack books on the market. The most powerful systems track aces as well as 10s.
The most common counting system simply assigns a value of plus-one to 3s, 4s, 5s, and 6s and minus-one to 10s, jacks, queens, and kings. All other cards are treated as neutral. Every time a 3 through 6 is dealt, add one to the count. Every time a 10-value card is dealt, subtract one. The total is called the running count. For example, if ten 3s through 6s have been played and only four 10s, the running count is plus-six. This needs to be normalized to the number of decks in the game, which is done by dividing by the approximate number of decks remaining in the shoe or in the dealer's hand. In a six-deck game, if the running count is plus-six and about three decks are left in the shoe, divide plus-six by three to get a "true count" of plus-two.
The final step is to adjust the bet to the count. In this simple version, if your beginning bet is one unit of $5, when the true count reaches plus-2, bet $10; at plus-4, bet $15, and at plus-6, bet $20.
A few words of warning: Because you are increasing your bet whenever the deck is favorable, playing with a counting system requires a much larger bankroll than betting the same amount every hand -- flat betting. You may be perfectly comfortable buying 10 bets' worth of chips -- $10 at a $1 table or $50 at a $5 table -- when flat-betting, but figure on at least 30 bets' worth when counting cards.
Card counters, just like any basic strategy player, lose more hands than they win no matter how good they are. They hope to more than make it up by winning larger bets in favorable situations. But sometimes the favorable situations just don't come -- it's possible to count down six-deck shoe after six-deck shoe without ever coming across a really favorable situation. And even on positive counts, sometimes the cards just turn the wrong way. There are no guarantees, not even for those who know the count and know what to do.
Finally, if the casino thinks you're counting cards, it can take measures. Nowhere in the country is card-counting illegal, but in Nevada the courts have held that the casinos are private clubs entitled to enforce their own rules, and the casinos can bar counters from playing. In other states, players can't be barred, but the casinos can increase the percentage of cards cut out of play to render the count less accurate. They can also take measures to make the player uncomfortable -- such as having a supervisor behind the table stare directly at the player while another supervisor stands at the player's shoulder from behind. If you're going to attempt to count cards, learn at home first. Deal cards to yourself or practice on a computer. Keep practicing until you're accurate every time, without moving your lips, with no brow-furrowing concentration, and without giving any other telltale signs of counting. Limit the size of your bets to a one-to-eight-unit range. A larger range will spark the casino's suspicions. And limit the length of your sessions. Don't play more than one hour in one place when counting cards.
If you wanted to increase you bet but do not count cards, you follow these guidelines:
A $5 bettor could begin a simple progression by increasing the bet to $10 after two wins in a row. After winning two consecutive hands at the $10 level, the player would increase to $15, and so on. After any loss, the player brings the bet back down to its original level.
The progression kicks in after two consecutive wins, so that the player never loses money on any sequence that begins with a win. If, after two $5 wins, the player loses the $10 bet, he is even. A third consecutive win guarantees a profit for the sequence.
Winnings can mount fast. If a player betting a flat $5 a hand wins six hands in a row, winnings total $30. The progression bettor has won two hands at $5, two at $10, and two at $15 for $60.
However, the system has two major problems. The progression usually ends with a loss on the largest bet in the sequence. And in any sequence that starts with two wins but shows a loss on the third hand, the progression bettor is worse off than the flat bettor. The progression bettor would be even after two $5 wins and a $10 loss; the flat bettor would show a $5 profit after two wins and a $5 loss. And a two-wins-and-a-loss sequence happens a lot more often than six consecutive wins.
Blackjack is a great game for casino novices. It is more engaging that a slot machine, but is much less complex than poker. Still, blackjack can be a favorite of card players at all experience levels. Now that you have the tools you need to become a better player, it's time to hit the tables.