The easiest method for a cheat, hard or soft, requires no ability of manipulation, but rather the profound nerve to blatantly cheat. Such methods include miscalling of hands, shorting the pot, and peeking at cards. Such cheating should not be tolerated. However, it is very difficult to prove because when confronted the cheat often calls the cheating an honest mistake. A simple and fair way to go about preventing this kind of cheating is to simply follow the rules. For example, "Cards Talk" is the common expression for the rule that no matter what the player says, it's the cards that determine who wins the pot. While it's barely legal to call a bad hand a full house in the hopes that people will give up, the players should want to see this hand, after all, they paid to look at it. Should such honest "mistakes" occur, it is best to ask the player to leave for that evening. If it was an honest mistake, he is in no condition to play poker (put aside your greed on this one - he will come back). If he did mean to cheat, he can't do it from outside the game and is unlikely to come back.
The minimal skill methods of cheating occur far more often then you might suspect. It is common for a player who has folded to appoint himself tender of the pot, stacking chips, counting them, and delivering them to the winning player, just so he doesn't have to get up. Nobody seems to notice the chip palmed in the hand of this helpful player. This is called check-chopping. This happens a lot. Once again, the answer is to follow the rules. Only at the showdown should a player touch the pot. In fact, it is a considerate player who obeys the rule concerning placing chips in the pot; The player does not throw the chips in the pot (splashing) but places them in a easily counted stack in the center of the table.
Cheating can happen even when the cheat does not have the deal. In draw, a player can discard two cards, throwing these two in the pile of discards so as to avoid counting (or if there is no pile, throw them on top of another player's discards), while calling for three. Not only does the cheat get the one card advantage in this hand, but before the showdown, he can ditch this extra card in his lap or vest, and thereby retain this one card advantage throughout the game. In this case, it is the dealer's job to regulate the discards, and to ensure the fairness of the process. In a way, this is the most fair. In exchange for the huge positional advantage the dealer has, he has responsibilities to occupy his time.
The most known method of cheating is marked cards. The cards are printed or altered such that the cheat can know their value while only looking at the back. The ways of marking are FAR too numerous to mention, but certain broad types can be mentioned. A common way of marking cards are making marks on a round design on the card so as to be read like a clock (an ace is marked at one o' clock and so on until the king which is not marked). Shading a card by putting it in the sun or scrathing the surface with an razor are ways to mark an already printed deck. Much talk and advertisement has been about concerning "colored readers", that is, marked cards that can only be read with the use of color filtered glasses or contact lenses. While such decks are available, they are painfully obvious to the observant poker player. Many cheating authorities mention the idea that while wearing contact lenses they always slip off-kilter to the pupil, therefore a red (the most common color) cresent will be visible on the sclera around the iris. "Juice" is a substance used to mark cards in a subtle way so as to avoid detection. Apparently one has to be "taught" to read juice patterns, but once taught, one can read (hence the term for marked cards "readers") them from across the table. An easy way to protect yourself from marked decks is to as the cheats say "Go to the movies". The idea is to flip through the cards rapidly, treating the deck much like a movie flip-book. If there is any difference in the cards, they should become rapidly apparent. Decks can also be marked while playing. A cheat can hold his hand in such a way that it will bend or buldge in a position that the cheat can read from across the table (called a crimp). In this case one should remember it is stipulated in the rules that any player may at any time request a new deck.
A cheat with moderate skill always has the option to hand-muck, that is, switch their hand with one they have secreted on them elsewhere. This may also be done with a confederate (see Collusion). Mechanical devices have been INVENTED for the purpose of switching hands. Though such machines are outdated, the modern equivalents (clips that hold cards on the underside of the table) should not be overlooked. The "hands above the table" house rule is recommended to prevent this. If it is done above the table, then anyone at the table can see it. This type of cheat runs the risk that he plays the same card as someone else at the table; at which time there must be a cheat at the table. Most people, not wanting to point fingers, will just end the game for the evening.
Never deny that a skilled cheat may deal a card from any place in the deck. A skilled cheat can deal the second card, the bottom card, the second from bottom card, and the middle card. The idea is to "cull", or to find the cards one needs, place them at the bottom, top, or any other place the cheat wants, then false deal them to himself or his confederate. Suppose the cheat is next to deal. In the previous showdown, there are four sevens in different hands. The cheat pick up the cards so that all four sevens end up on the bottom of the deck. He then false shuffles the deck and deals himself the four sevens off the bottom of the deck. There are lots of tells as to this kind of cheating:
Ok, with all this high power slight of hand, the cheat still won't win money with four sevens if everyone else has a bust, so the cheat stacks two hands. Obviously the cheat will get the better one. Let's say he has two hands one on the bottom of each half of the deck, ready to shuffle (let's say four kings and four aces). All the cheat has to do is to shuffle the two halves PERFECTLY, that is, alternating from one half to the other. When done with the whole deck this is called a faro shuffle. This places in alternating order on the bottom of the deck from the bottom up the cards K,A,K,A,K,A,K,A, and the rest of the deck. He can then false shuffle to his heart's content. and begin dealing. When he gets to the player who has the most money, he deals that player the bottom card. He deals himself bottoms too. This places the big fish with four kings, a real betting hand, and the cheat with four aces, hence the cheat cleans up. This is called the double duke. The best way to foil mechanics of this nature is to burn them, to watch their hands at all times and to always insist on a cut. This may not prevent them from cheating, but it forces them to undo the cut - a difficult and dangerous move. Only world class cheats will undo a cut while being burned. Note: no other shuffling or cutting is allowed after EVERY player is offerd the option of cutting. A cheat may bend the entire deck so as to reveal where the cut was, so that his confederate sitting to his left may undo the cut or he may do so himself should the appropriate distraction present itself.
This pales in comparison to the granddaddy of all cheating - the "cold deck". After all the shuffling and cutting has been done (everyone nicely pacified) the cheat can switch the deck for one he has stacked beforehand so that everyone has a real betting hand, but, of corse, the cheat has the best one. Such a move is difficult, and may (I may stress) require distraction, but once done, no other sleights are necessary to win. The only defense is to simply always watch the deck. Many players believe that it is bad luck to look at your cards before the dealer is finished so you won't miss your opponents' reactions to their cards by burning the dealer.
In conclusion, it is generally a good idea to be wary while playing a cutthroat game for money. It is NEVER a good idea to take the notion that since you know the way in which people cheat, that you cannot be cheated. You can. Many of the greatest gamblers in history have been cheated out of large amounts of money. I realize that I have left so much out as far as actual cheating methods, but entire volumes have been written on this subject alone.