Counting cards in blackjack is actually the easy part of the game. The harder part is memorizing the basic betting strategy that you should apply after you actually know the count.
So there are a bunch of different ways to count cards at blackjack, but by far the most popular and also the simplest one is the Hi-Lo count. All you have to do is assign values of -1, 0, and +1 to cards in the deck and keep track of the running count.
Values of cards are as follows:
High cards (T, J, Q, K, A) = -1
Mid cards (7, 8, 9) = 0
Low cards (2, 3, 4, 5, 6) = +1
This way you keep track of whether the remaining deck or shoe is high card rich or low card rich. In general, a high-card deck is more favorable to the player, so that is when you should bet more, and a low-card deck is favorable to the dealer, so you should keep your bets low. So if the count is positive, preferably high positive, there are more high cards left.
There is also one more trick to counting cards in blackjack with this method. Since there is usually more than one deck in use, you have to get a true count out. This is actually not that important and you can do perfectly fine without it, but it still helps. All you have to do is divide your count by the number of decks still in use. So if your count is +5 and there are 3 decks left, you divide 5/3 = 1,66 and that is your true count.
The tough part of it is applying a winning betting strategy to your count. There are a bunch of different charts out there that give you the betting strategy based on the count and your and the dealer’s hand. The one I really like is the blackjack calculator here and another one here. It gives out a chart for pretty much any blackjack game you can imagine, just fill in the specs and it will produce it.
Since this is a beginner guide, If you would like a more whole and in-depth look at card counting in blackjack go here.