There are two ways to get ahead. You can work the system or you can beat the system.
Beating the system usually involves some sort of subterfuge. Once everyone knows how you beat the system, the system adjusts and changes the rules, making it difficult for you to repeat the feat again. When card counters beat the system in Las Vegas, they weren't breaking the rules, but the system didn't care. They just increased the number of decks in use so it would be more difficult and less lucrative.Common misconception.
Actually, increasing the number of decks in the shoe makes winning easier for the counter. It's how often the shoe (decks) are shuffled that makes it more difficult to count. And, a two-deck shoe will more be shuffled more often. This point was made in the audiobook I listened to recently, "21: Bringing Down the House: The Inside Story of Six M.I.T. Students Who Took Vegas for Millions."
First you have to learn what card counting is all about (scroll down to Lesson #2). This lesson is taught by Jeff Ma, the person who led the MIT team in the casinos and was fictionally portrayed in the book mentioned above, which was subsequently made into a movie that conveniently omitted any explanation of this technique. (Was this a deal made with the casinos so that they could film on location?)
The way card counting works in 21 is that you gain a very slight advantage if you know the count is strongly positive, let's say, +16, which means more high-value, picture cards are bound to follow. This gives the advantage to the player. You've been betting the minimum all along, now you increase your bet to take advantage of the better odds. This is a tipoff to the casino that you're counting cards, btw. Then you use Basic Strategy to play your hand. There's also a formula for determining how much you should bet, which you can also find on Jeff's Web site mentioned above.
This is why you need team play. You need people at several tables playing, and then when anyone finds the count to be strongly positive, they give the team leader a hand signal, and he swoops in as a high roller so the counter doesn't get detected.
Disclaimer: I've never been in a casino, but I have very eclectic reading tastes.