There has been a great deal written on card counting and nothing that I am about to say today is novel in any way shape or form. there are a number of serious resources out there for aspiring blackjack players, such as the blackjackinfo.com archived forums (and the rest of that site is all gold as well), bj21.com (stanford wong's site) as well as blackjackforumonline.com (the info is a touch dated but still valuable and certainly an interesting read at the least).
The theory behind card counting is this. Because the house edge of blackjack using basic strategy is so small, usually .5%, then the removal of certain cards from the shoe (as they are played) can alter the odds of the game. So a six being played for example may shift the odds in favour of the player by .1%, leaving the house edge at only .4%. If over the course of the shoe more low cards are dealt out than high cards, the advantage climbs. Typically card counters wager with a 1 to 2% advantage. And as Benny Binion said "give me a tenth of a percent and enough time and I will break any man in the world". High cards favour the player because they complete our key double downs and because blackjacks pay us 3:2.
How to count cards.
The first thing you must do is learn basic strategy. Basic strategy changes depending which casino you are playing. There is actually a game which teaches you basic strategy.
https://www.blackjackinfo.com/blackj...ategy-trainer/
So you just go there, plug in the rules for the casino you will be playing at, and you play the game and it tells you every time you make a mistake. So if you play it for a few hours you should have that particular basic strategy rule set mastered. It is vital not to make any basic strategy mistakes, since even a few errors can cancel out your edge. This simulator is also countable.
At this point you will want to invest in a discard tray and dealing shoe as well as decks of cards. You want to simulate the casino environment as best as you can before you start risking your money.
So once you have mastered basic strategy, the next thing is to learn how to count. There are two very simple drills that can help you here. The first is to take a deck of cards. Place one card face up on the table. Now, at this point you are not even counting. What you are doing is associating tag values. There are three tag values. Plus. Minus. Neutral. Plus is 2, 3, 4, 5 and 6. Neutral is 7, 8 and 9. Minus is T, J, Q, K and A. So you simply flip through the deck one at a time and say to yourself either "PLUS" "MINUS" or "NEUTRAL" depending on what card it is. And the point here is simply to establish a connection between the card and it's tag value. You are training yourself to think of these cards as simply PLUS, MINUS or NEUTRAL. And you do this until you are totally comfortable with it, however long it takes. Probably shouldn't take long, but if you feel like you need more time doing it, keep doing it. It is far better to be patient and master this activity carefully as opposed to rushing through it and going broke.
The second drill is to flip through a deck of cards and now keep count. So you start off with a five, and think to yourself 'ONE'. Then you get a 7, which is neutral, so you think again 'ONE'. Then you get a 4, and you think to yourself 'TWO'. Then a jack so you think 'ONE'. So just flip through the cards slowly, and keep count. If you did it correctly, then you should be able to predict the last card as it will be the opposite of your count. That is, if your count at the end is plus one, then the card will be a high card. IF it is -1 it will be a low card.
So once you can count, you then need to know about the true count. So what we have discussed previously was the running count. It goes up or down depending on the cards dealt. But what we are really concerned with is the true count, or count per deck. So to get the true count you divide by the running count by the decks remaining. Let's say the dealer has dealt out 2 decks of a 6 deck shoe. That is 4 decks remaining. So if the running count was 7 you would divide 7 by 4 and come up with a True Count of 1.75. This is a roughly 1% advantage for the player depending on rules. All of our betting and playing decisions are made with True Count figures. So this is something you can practice as you play through a shoe, keeping the running count and also converting to the true count. It will be difficult initially, but eventually you will do it instantly, which is why it is ABSOLUTELY VITAL that you spend time practicing at home until you are perfect. Do not just rush out to a casino. Practice, practice, practice.
Deviations :
There are many deviations from basic strategy. Most of the gain can be captured by 20 or core ones which I will enumerate but if you become a serious blackjack player you should always keep learning more.
16 v T : 0. Any time the running count is positive stay on 16 vs T.
15 v T : +4. Any time the true count is +4 or higher, stay on 15.
(more to come later)