Another strategy that blackjack players use to help them on their road to victory (and hopefully a lot of money!) is counting cards. Having an idea of what cards are still left to come can help you make smarter bets. When there are many more high cards in the deck than low cards, there are more chances that the dealer will bust, since he is required to hit if his cards total less than seventeen. Likewise, if there are more low cards left in the deck than high cards, the dealer has a better chance of beating you. So if you can determine at least roughly what cards remain in the deck, you'll know whether you should be betting more money or keeping your bets small.
When playing with one or two decks, you may find it easy to memorize the cards that have been played, furthering your chances of winning as the deck(s) are depleted, because you know what cards are left. With multiple decks and in casinos, there are variations on counting cards that help a player to maximize his earnings.
Casual Card Counting
Casual card counting is a method that requires no mathematics and hardly any concentration. The object is just to observe the flow of cards coming from the deck. If you notice that a good number of face cards and aces have been played recently, it's time to rein in your bet. If a lot of low cards have been played, it's a good time to up your bet. Look for obvious extremes. If the cards are flowing out relatively evenly, you'll want to employ some of the betting strategies listed later.
High-Low Card Counting
The high-low system of counting cards is a popular method for keeping track of what is going on with the decks. In this system, you apply a value of –1 to any high cards (aces, face cards, or tens). A value of +1 is applied to low cards (two, three, four, five, or six). A value of 0 is assigned to any middle cards (seven, eight, or nine). As each hand is dealt, keep a running tally of points, and make your wagering decisions based on what the total is. When the total is positive, the advantage is yours, and you should increase your wager. When the total is negative, the advantage is to the dealer and you should decrease your wager. As the game progresses through the decks, the accuracy of the running tally becomes greater, and the wagers can be increased or decreased accordingly.