This is a strategy hard to manage even by the experienced players. The basics what happens when you're counting cards is that you keep in mind an accurate record of the cards that have been played. This allows you to have a relatively good idea of which cards remain in the shoe.
Short History
In 1962 Edward Thorpe made public for the first time this strategy in his book "Beat the Dealer". Because this book gained the interest of the most gamblers, many casinos made new rules that were not favorable for the players. They refused then to play after these rules and the casinos implemented better rules, along with certain changes that have remained in place to this day. Thorp's system was refined and even replaced by improved counting systems that continue to be developed even now.
The Logic
In a full deck is 52 cards. If you have a 4 out of the 52 cards you still have a chance to be dealt a queen from this full deck. If all the Queens from the deck were already dealt, than is absolutely logic that you wont get any chance of getting a Queen. Card counters use this information about cards that have already been played to try to assess how favorable the remaining cards are.
A simple system for counting cards
This simple system for counting cards is the hi-lo system and usually it is used by the inexperienced players. This system works on the idea in which you need to keep track of the number of high, low and neutral cards remaining in the pack. The cards are assigned a value as follows:
2,3,4,5,6 (low cards) = +1
7,8,9 (neutral cards) = 0
10, jack, queen, king, ace (high cards) = -1
Players try to keep a mental total or running count of all the cards that have been dealt or exposed by adding and subtracting the values of the cards. For example, a sequence of cards with the next values: 3, queen, king, jack, 8, 4, 3, king, 9, 10, results in a total of -2. When the count is negative, the deck is said to be rich in low cards and thus favoring the dealer. When the count is positive, the deck is said to be rich in high cards and favoring the player. To capitalize on a favorable count, the card counter will then make large bets when the deck is "positive" and small bets when it's "negative".
Why counting cards is not such a good prospect these days
- To use counting card strategy at a table in a casino it's not illegal but usually casinos ask the suspected counters to leave the table or to choose another gambling game to play.
- Casinos try to discourage counters, using several decks, shuffling the deck early or continuously reshuffling the deck. With these methods it will be harder for a counter player to count properly.
- If you can bypass those two obstacles above, then you're faced with the fact that counting is really a 'win some, lose some' technique that usually sees the counter suffering wild fluctuations in his/her bankroll. One minute he could be up hundreds, the next minute he's down by thousands. There's nothing guaranteed thus counters have to ante up and make sure they've got enough money to weather the losing streaks that may come.
Counting cards online
Online casinos almost always use multiple decks and continuous shuffling in their blackjack games and because of that it's impossible for you to use the counting cards strategy.