Cards counting techniques in blackjack

The counting cards strategy is based on probabilities, and accountability of all cards in the deck or decks. Unfortunately there’s a small minus in this strategy: after some deliveries, the dealer throw away the non played cards left, and the next delivery can be made from a new mixed deck. Before the dealer mixes the cards, the half or three fourths of the cards could be thrown away. This means that among the thrown cards could be the cards that bring advantage to the player. And the cards your strategy was based on. The counting cards system counts the 10 points cards delivery probability, based only in the card still founded in the deck.
The most general and simple counting system, gives the cards some define values:
All cards from twos to sixes have a value of +1.
All cards from tens to aces have a value of -1.
Sevens, eights and nines have a value of 0.
As the player sees the played (consequently thrown away) card, he counts the values of these cards. The starting point is 0; this counting can turn into negative and positive values. If the first delivery from the deck has a two (+1), a nine (0), a king (-1), an ace (-1), a ten (-1), and a jack (-1), the present count will be -3 (minus three).
The higher the present count is, the lower cards were played, which means a higher number of high cards in the deck. Why is that important to us? Remember, the basic strategy system is based on expectation, that the next card will have a value of 10 points. If you know that the higher cards percent is getting bigger than usual, that’s a deduction, and that means that the whole strategy is getting more effective.