The Hi-Lo Counting System
As discussed earlier, card counting is centered on keeping a “running count” of the deck. When you first sit down at the table, you start with zero. Every time you see a card, you will add to this value, subtract from it, or not change it at all. The Hi-Lo system is known as a “single-level” or “level-one” system, because this number will never change by more than one for any given card. Its simplicity, combined with its effectiveness, make it one of the most popular card counting systems.
Skillfully keeping track of the running count is the first major hurdle to successful card counting. The game is fast paced, and if you seem detached from the table around you and are consistently delaying your move as you try and keep track of the running count, you will quickly come under suspicion.
Practice by getting a deck of cards, throwing them down on the table one at a time as quickly as you can manage, and keeping a running count in your head (remember, since Hi-Lo is a balanced system, you should always end with zero). Then try your hand at counting actual games, but don’t worry about adjusting your bet yet; just bet the minimum and keep the running count.
The True Count
Unfortunately, the running count quickly runs into problems with multiple decks in a game of blackjack. Let’s say that a particular game of blackjack is being dealt from ten decks. If the first hand shows a total of nine low cards, the running count is +9. However, there are still many low cards available to be dealt. To help get a better picture of the actual odds, players use the true count.
Officially, the true count is the running count divided by the number of decks yet to be dealt. For example, if in a ten-deck game 26 cards have been dealt, 9 ½ decks have not been dealt. If we use our previous running count of +9 and divide it by 9 ½, we get a true count of only +0.95. This true count gives a much better estimate of our actual odds, because it reflects how many cards are still waiting to be played. The higher the true count, the more you should bet. Below 0, always bet the minimum.
The exact amount of decks remaining can be counted as the game is played, but that adds yet another level of mental arithmetic that most people would find hard to keep up with. Instead, most card counters approximate half a deck for calculating the true count. When just starting out, full deck counts are an acceptable alternative. The more accurate the value used for remaining decks, the more accurate the true count, and the better you can estimate your odds. I came accross this site to practice card counting that you may find useful: http://www.countingedge.com/blackjack-card-counting-trainer.htm