Card counting can be a very useful skill when playing blackjack. But it is a skill that requires time, practice and patience to learn to the point of effectiveness. A good many novice players do not have the correct perception of what card counting is and what it does.
So we will start there, with what card counting is. Card counting is a skill in which the player mentally tracks the flow of cards. This is not an exact count; the purpose of card counting is to give players an idea of when there are more high cards left in the unplayed deck. This is discovered when the count a player is keeping has reached the point that more low cards have been played than high cards.
Once a player has the knowledge that more low cards have been played, leaving a greater number, and therefore likelihood, of high card being dealt, the player can begin raising their bets. Bets are raised at this point because there is a greater chance of being dealt a strong hand if not an outright natural blackjack. When the remaining deck is rich in high cards, there is a greater chance of the player winning, which is why bets are increased at this point.
To sum it up, counting cards in blackjack can give players a long-term advantage over the house by knowing when they are more likely to win, and raising their wagers accordingly.
Now. What card counting is not.
Card counting is not a short cut that will allow players to beat the house. Yes, it will allow players to tilt the odds in their favor, but it is not an instantaneous happening. It is not a flashy skill to be thrown around the casino.
To be successful with card counting in blackjack, time and patience must be applied while learning the counting system of your choice. Players who utilize card counting when playing blackjack also have to understand that they are not going to win every single hand, but that they will win more over the long run.