In a card game like blackjack, it is beneficial to the player to know what to expect in regards to the remaining cards in the deck. Knowing whether or not the deck holds a majority of low cards or high cards can aid the player in making important wagering decisions.

There is no single method used to count cards. Some methods are more complicated than others, and not all of them involve memorizing all the cards that have been played. The basic method used to count cards is known as the Hi-Low system. With this, each card has a value. Cards 6 and lower (not included the ace) are given a positive one value. Cards 10 and above (including the ace) are given a negative one value. All cards in between (7, 8 and 9) are given no value and are ignored in the card counting process.

Each time a card is dealt in the game, the card's value it noted. Each of these card's values are added to each other, making up a running total. The value of the running total indicates to the player which cards remain in the deck. It helps the player make decisions like whether or not to take another hit, or when and if they should change their bet.

A minus count is a running total that has a value that is lower than zero and indicates that the deck has a high volume of low-value cards. In this case, the dealer has less of a chance of busting early and both the players and the dealer have less of a change of scoring a blackjack. The odds, however, are more in favor of the dealer. In the case of running total being equal to zero or awfully close, the deck is said to be neutral.

A plus count is a running total that has a value higher than zero. This indicates that the deck still has a high volume of high-value cards and the odds are in the players favor. The odds rest in the player's favor because the higher the number of high-value cards there are, the more likely it is that the dealer will bust. This is because the dealers have rules that restrict them. One such rule requires the dealer to take another hit if their hand has the value of 16 or less. A player, on the other hand, has the choice to take another hit or to stand. Also, the player gets paid out 50% more if they get a blackjack. The dealer is not privy to this pay out; they simple receive the original wager. This is why high value cards benefit the player more so than the dealer.

These reasons justify the systems that count cards, as they aid serious player in making important betting decisions. The more familiar you become with these systems, the more likely you will find that they work in your advantage.