Counting is achieved using a + and – system. The simplest and most popular counting system assigns a value of +1 to a 3, 4, 5 and 6, and a value of -1 to kings, queens, jacks and 10s. Every other card is considered to be worth 0. In practical terms, this means that each time a card between 3 and 6 is dealt, one is added to the total count. Each time a card with a value of ten is dealt, one is subtracted. The last stage is to adjust your bet to match the count. That means that once your count reaches +2, double your bet, then once it has reached +4, triple it, and then once it has reached +6, quadruple it.
The downside to counting cards is that you need a large bankroll since you will be increasing your wager when the deck becomes favourable, and of course, even card counters will lose more hands than they can win, regardless of how good a player they are. Their hope, however, is to make the amount up by winning a larger bet in a favourable situation. Yet, there is no guarantee that a favourable situation will come along as there can be no guarantees in gambling.