Counting cards isn't cheating at blackjack. (Thought I'd get that out of the way immediately.) Card counting is simply good strategy; you use the information available to yourself and to everyone else at the table to make intelligent decisions about the best way to play your hands, and the best amount to bet on any given hand.
That being said, the casinos sure don't like card counting. They reserve the right to decide who can and can't play at their casino too, and if you're a good card counter who gets caught, you could easily find yourself "barred" from playing at a given casino.
There are ways to cheat at blackjack though, and we don't recommend any of them. Actually cheating at a casino game can get you in big trouble with the law, and you probably don't want to tangle with the security at a casino either. This is more of an intellectual discussion of cheating as it pertains to blackjack, rather than a "how-to" manual.
One way players try to cheat at blackjack is by marking the cards in some way as they play. The advantages of knowing what the dealer's face down card are obvious.
A popular method for marking cards is by having sharp, long fingernails, and making a mark on certain cards using the fingernail to scratch the card.
Big trouble if someone gets caught doing this. The kind of trouble you don't want to mess with.
If you're a master of sleight-of-hand, you might be tempted to switch the actual cards in your hand with a card or two that you happen to have up your sleeve. Again, hard to avoid getting caught, and big trouble for you if and when you do.
Theoretically, someone could bribe a dealer to fix a blackjack game somehow. The problem is that a dealer who can be bribed by a player can probably also be bribed by the casino to cheat, and a casino that cheats its players is probably going to be out of business quickly. The casinos don't have to cheat anyway, because they already have an irreversible mathematical advantage against players who aren't counting. The same goes for online casinos. Is online blackjack rigged? The fair answer is no.
There's an old saying in the are of the country where I'm from: "Cheater never win, and winners never cheat." My advice to you is don't cheat.
For one thing, your integrity is worth far more than any money you'd make by cheating a casino.
For another, your health, well-being, and freedom are worth far more than any money you'd make too.
Please note that the information on this page is for entertainment and educational purposes. We don't condone cheating, this isn't a "how-to" guide, and we're not offering legal advice.