Counting cards at Blackjack is a learned skill and frowned upon by casinos. In fact if they think you are doing this and winning they may bar you from playing Blackjack in their facility. What is card counting and why are the casinos leery of players who can count cards? There is no way this could be considered cheating, but a player who is good at this method is treated like a cheater.
The reason the player is feared who can do this with skill and discipline is simple. It puts the odds in the player’s favor. The house edge in the game is destroyed when the deck is rich in face cards. The odds for the rest of the shoe will remain with the player to win more bets than the dealer due to the fact that he can wave off hitting a card on a break hand. The dealer must hit any hand lower than soft 17 (Ace and a six). A rich shoe in face cards means the dealer has a higher chance of busting their hand.
There are several good books on this method of play, which are easily found on the Internet or in any bookstore for gamblers. The idea is to count the shoe down by keeping track of the cards as the dealer shows them. You know how many face cards are in a six-deck shoe...