Because blackjack, unlike other games, has an element of player choice, players can actually reduce the casino advantage to a small percentage by playing what is known as basic strategy. This strategy determines when to hit and when to stand, and also determines when doubling down or splitting is the correct action. Basic strategy is based on the player's point total and the dealer's visible card. There are slight variations in basic strategy depending on the exact house rules and the number of decks used.
In some LV Strip casinos you may still be able to find the older version of the multi-deck shoe game, where dealer stands on soft 17; those are usually high minimum ($50 or more) tables. This version is much more advantageous to the player, but requires a slightly modified basic strategy table (such tables can be generated using the external links).
Basic strategy provides the player with the optimal play for any blackjack situation, based on millions of hands played in the long run. However in the short run, as the cards are dealt from the deck, the remaining deck is no longer complete. By keeping track of the cards that have already been played, it is possible to know when the cards remaining in the deck are advantageous for the player.
Card counting creates two opportunities:
- The player can make larger bets when he or she has the advantage. For example, the player can increase the starting bet if there are many aces and tens left in the deck, in the hope of hitting a blackjack.
- The player can use information about the remaining cards to improve upon the basic strategy rules for specific hands played. For example, with many tens left in the deck, the player may double down in more situations since there is a better chance of making a strong hand.
There are several card counting systems which do not require that the player remembers which cards have been played. Rather, a point system is established for the cards, and the player keeps track of a simple point count as the cards are played out from the dealer.
Depending on the particular blackjack rules in a given casino, basic strategy reduces the house advantage to less than one percent. Card counting typically gives the player an advantage of 0.5 to 1.5% over the house. To counter card counting, some casinos play with multiple decks.
In most US jurisdictions, card counting is legal and is not considered cheating. However, most casinos have the right to ban players, with or without cause, and card counting is frequently used as a justification to ban a player. Usually, the casino host will simply inform the player that he is no longer welcome to play at that casino. Players must be careful not to signal the fact that they are counting. The use of electronic or other counting devices is usually illegal and almost always prohibited by the casino.
Basic strategy is based on a player's point total and the dealer's visible card. A player's ideal decision may depend on the composition of his or her hand, not just the information considered in the basic strategy. For example, a player should ordinarily stand when holding 12 against a dealer 4. However, in a single deck game, the player should hit if his or her 12 consists of a 10 and a 2; this is because the player wants to receive any card other than a 10 if hitting, and the 10 in the player's hand is one less card available to cause a bust for the player or the dealer.
However, in situations where basic and composition-dependent strategy lead to different actions, the difference in expected value between the two decisions will be small. Additionally, as the number of decks used in a blackjack game rises, both the number of situations where composition determines the correct strategy and the house edge improvement from using a composition-dependent strategy will fall. Using a composition-dependent strategy only reduces house edge by 0.0031% in a six-deck game, less than one tenth the improvement in a single-deck game (0.0387%).
There are well-established techniques other than card counting that can swing the advantage of casino blackjack towards the player. All such techniques are based on the value of the cards to the player and the casino, as originally conceived by Edward O. Thorp. One such technique, mainly applicable in multi-deck games (aka shoes), involves tracking groups of cards (aka slugs, clumps, packs) during the play of the shoe, following them through the shuffle and then playing and betting accordingly when those cards come into play from the new shoe. This technique, which is admittedly much more difficult than straight card counting and requires excellent eyesight and powers of visual estimation, has the additional benefit of fooling the casino people who are monitoring the player's actions and the count, since the shuffle tracker could be, at times, betting and/or playing opposite to how a straightforward card counter would.
Arnold Snyder's articles in Blackjack Forum magazine brought shuffle tracking to the general public. His book, The Shuffle Tracker's Cookbook, mathematically analyzed the player edge available from shuffle tracking based on the actual size of the tracked slug.
Jerry L. Patterson also developed and published a shuffle-tracking method for tracking favorable clumps of cards and cutting them into play and tracking unfavorable clumps of cards and cutting them out of play.
Other legal methods of gaining a player advantage at blackjack include a wide variety of techniques for gaining information about the dealer hole-card or the next card to be dealt.
Card tracking is restricted when the casino uses a half-cut, or what is known inside houses as 'The Big C'. This is when the shoe is cut halfway, meaning that only half of the shoe will be played, so on an 8-deck shoe, only 4 decks will be played and thereafter shuffled. As card tracking relies on the principles of elimination, the half-cut makes it virtually impossible to eliminate or predict the remaining cards. Another exception to card tracking is the introduction of automatic shuffler machines, thereby making it impossible to track cards because the shoe is non-stop.