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Poker strategy is a complex subject. This article only attempts to introduce basic strategy concepts.

The fundamental theorem of poker

The fundamental theorem of poker states that every time you play your hand the way you would if you could see your opponent's cards, you gain, and every time your opponent plays his cards differently from the way he would play them if he could see your cards, you gain.^[1] This theorem is the foundation for many poker strategy topics. For example, bluffing and slow-playing (explained below) are examples of using deception to induce your opponents to play differently than they would if they could see your cards. There are some exceptions to the fundamental theorem in certain multi-way pot situations, as described in Morton's theorem.

See the articles on the fundamental theorem of poker and Morton's theorem for more details.

Pot odds and poker probabilities

The relationship between pot odds and odds of winning is one of the most important concepts in poker strategy. Pot odds are the ratio of the size of the bet required to stay in the pot to the size of the pot.^[1] For example, if a player must call a $10 bet for a chance to win a $40 pot (not including his $10 call), his pot odds are 1-to-4 (20% probability). To have a positive expectation, a player's odds of winning must be at least equal to his pot odds. Continuing the previous example, if the player's odds of winning are also 1-to-4, if he plays the pot five times, he puts in $10 five times, loses four times and wins $50 once (breaking even).

See the article on pot odds for a more about including manipulating pot odds, implied pot odds, effective implied odds, and reverse implied odds.

See the article on poker probability for more about determining the odds of having (or improving to) the best hand.

Deception

By employing deception, a poker player hopes to induce his opponent(s) to act differently than they would if they could see his cards. Bluffing is a form of deception to induce opponents to fold superior hands. Against observant opponents, it is necessary for a player to bluff sometimes to induce opponents to call his bets when he actually does have a superior hand. If opponents observe that a player never bluffs, they won't call his bets unless they have very good hands. Slow-playing (also called "sandbagging") is deceptive play in poker that is roughly the opposite of bluffing: betting weakly with a strong holding rather than betting strongly with a weak one.

See the article on bluffing for more about bluffing strategies, semi-bluffs, and optimal bluffing frequency.

See the article on slow playing for more about slow playing strategies.

Position

Position refers to the order in which players are seated around the table and the strategic consequences of this. Generally, players in earlier position (who have to act first) need stronger hands to bet or raise than players in later position. For example, if there are five opponents yet to act behind a player, there is a greater chance one of the opponents will have a better hand than if there was only one opponent yet to act. Being in late position is an advantage because a player gets to see how his opponents in earlier position acted (which provides the player more information about their hands than they have about his).

See the article on position for more about positional play.

Reasons to raise

Unlike calling, raising has an extra way to win: opponent(s) may fold. An opening bet may be considered a raise from a strategy perspective. Sklansky gives seven reasons for raising, summarized below.^[1]

To get more money in the pot when a player has the best hand: If a player has the best hand, raising for value enables him to win a bigger pot.

To drive out opponents when a player has the best hand: If a player has a made hand, raising may protect his hand by driving out opponents with drawing hands who may otherwise improve to a better hand.

To bluff or semi-bluff: If a player raises with an inferior or drawing hand, the player may induce a better hand to fold. In the case of semi-bluff, if the player is called, he still has a chance to improve to a better hand (and also win a larger pot).

To get a free card: If a player raises with a drawing hand, his opponent may check to him on the next betting round, giving him a chance to get a free card to improve his hand.

To gain information: If a player raises with an uncertain hand, he gains information about the strength of his opponent's hand if he is called. Players may use an opening bet on a later betting round (probe or continuation bets) to gain information by being called or raised (or may win the pot immediately).

To drive out worse hands when a player's own hand may be second best: Sometimes, if a player raises with the second best hand with cards to come, raising to drive out opponents with worse hands (but who might improve) may increase the expected value of his hand by giving him a higher probability of winning in the event his hand improves.

To drive out better hands when a come hand bets: If an opponent with an apparent come hand (drawing hand) bets before a player, if the player raises, opponents behind him who may have a better hand may fold rather than call a bet and raise. This is a form of isolation play.

Reasons to call

There are several reasons for calling a bet or raise, summarized below.

To see more cards: With a drawing hand, a player may be receiving the correct pot odds with the call to see more cards.

To limit loss in equity: Calling may be appropriate to when a player has adequate pot odds to call but will lose equity on money contributed to the pot.

To avoid a re-raise: Calling denies the original bettor the opportunity of re-raising.

To conceal the strength of a player's hand: If a player has a very strong hand, he might smooth call on an early betting round to avoid giving away the strength of his hand on the hope of getting more money into the pot in later betting rounds.

To manipulate pot odds: By calling (not raising), a player offers any opponents yet to act behind him more favorable pot odds to also call. For example, if a player has a very strong hand, a smooth call may encourage opponents behind him to overcall, building the pot. Particularly in limit games, building the pot in an earlier betting round may induce opponents to call future bets in later betting rounds because of the pot odds they will be receiving.

To set up a bluff on a later betting round: Sometimes referred to as a long-ball bluff, calling on an earlier betting round can set up a bluff (or semi-bluff) on a later betting round.^[2]

Gap concept

The gap concept states that a player needs a better hand to play against someone who has already opened the betting than he would need to open himself.^[3] The gap concept reflects that players prefer to avoid confrontations with another player who has already indicated strength, and that calling only has one way to win (by having the best hand), whereas opening (or raising) may also win immediately if your opponent(s) fold.

Sandwich effect

Related to the gap effect, the sandwich effect states that a player needs a stronger hand to stay in a pot when there are opponents yet to act behind him.^[2] Because the player doesn't know how many opponents will be involved in the pot or whether he will have to call a re-raise, he doesn't know what his effective pot odds actually are. Therefore, a stronger hand is desired as compensation for this uncertainty.

Loose/tight play

Loose players play relatively more hands and tend to continue with weaker hands. Tight players play relatively fewer hands and tend not to continue with weaker hands. The following concepts are applicable in loose games (and their inverse in tight games):^[1]

Bluffs and semi-bluffs are less effective because loose opponents are less likely to fold.
Requirements for continuing with made hands may be lower because loose players may also be playing lower value hands.
Drawing to incomplete hands, like flushes, tends to be more valuable as draws will often get favorable pot odds and a stronger hand (rather than merely one pair) is often required to win in multi-way pots.

Aggressive/passive play

Aggressive play refers to betting and raising. Passive play refers to checking and calling. Unless passive play is being used deceptively as mentioned above, aggressive play is generally considered stronger than passive play because of the bluff value of bets and raises and because it offers more opportunities for your opponents to make mistakes.^[1]

See the article on aggressive play for more details.

Hand reading and tells

Hand reading is the process of making educated guesses about the possible cards an opponent may hold based on the sequence of actions in the pot. A tell is a detectable change in an opponent's behavior or demeanor that gives clues about his hand. Educated guesses about an opponent's cards can help a player avoid mistakes in his own play, induce mistakes by his opponent(s), or to influence the player to take actions that he would normally not take under the circumstances. For example, a tell might suggest an opponent has missed a draw and holds a weak hand, but a player also missed a draw and is sure his hand is even weaker. In this case, using the tell, the player may decide a bluff would be more effective than usual.

See the article on tells for more information.

Table image and opponent profiling

By observing the tendencies and patterns of your opponents, you can make more educated guesses about their potential holdings. For example, if a player has been playing extremely tight (playing very few hands), when they finally do enter a pot, you may surmise that they have stronger than average cards. Your table image is the perception of your opponents of your own pattern of play. You can leverage your table image by playing out of character and thereby inducing your opponent(s) to misjudge your hand and make a mistake.

Equity

A player's equity in a pot is his expected share of the pot, expressed either as a percentage (probability of winning) or expected value (amount of pot * probability of winning). Negative equity, or loss in equity, occurs when contributing to a pot with a probability of winning less than 1 / (number of opponents matching the contribution).

Example

Alice contributes $12 to a pot and is matched by two other opponents. Alice's $12 contribution "bought" the chance to win $36. If Alice's probability of winning is 50%, her equity in the $36 pot is $18 (a gain in equity because her $12 is now "worth" $18). If her probability of winning is only 10%, Alice loses equity because her $12 is now only "worth" $3.60.

If there is already money in the pot, the pot odds associated with a particular play may indicate a positive expected value even though it may have negative equity.

Texas hold'em example

Alice holds J♦ 7♠. Bob holds K♥ 6♠. After the flop, the board is 5♥ 6♥ 8♦. If both hands are played to a showdown, Alice has a 45% chance to win, Bob has a 53% chance to win and there is a 2% chance to split the pot. The pot currently has $51. Alice goes all-in for $45 and is certain that Bob will call. Alice's implied pot odds for the all-in raise are 32%. Bob's simple pot odds for the call are also 32%. Since both have a probability of winning greater than 32%, both plays (the raise and the call) have a positive expectation. However, since Bob has more equity in the pot than Alice (53% vs. 45%), Alice would have been better off playing the pot as cheaply as possible. When Alice raised, she gave up the difference in equity on the money she contributed to the pot.

Short-handed considerations

When playing short-handed (at a table with fewer than normal players), players must loosen up their play (play more hands) for several reasons:^[1]

There is less likelihood of another player having a strong hand because there are fewer players.
Each player's share of the forced bets increases because there are fewer players contributing to the forced bets, thus waiting for premium hands becomes more expensive.

Structure considerations

The blinds and antes and limit structure of the game has a signficant influence on poker strategy. For example, it is easier to manipulate pot odds in no-limit and pot-limit games than in limit games. In tournaments, as the size of the forced bets relative to the chip stacks grows, pressure is placed on players to play pots to avoid being anted/blinded away.^[4]

Notes

^ ^a ^b ^c ^d ^e ^f David Sklansky (1987). The Theory of Poker. Two Plus Two Publications. ISBN 1880685000.
^ ^a ^b Dan Harrington and Bill Robertie (2004). Harrington on Hold'em: Expert Strategy For No-Limit Tournaments; Volume I: Strategic Play. Two Plus Two Publications. ISBN 1880685337.
^ David Sklansky (2001). Tournament Poker for Advanced Players. Two Plus Two Publications. ISBN 1880685280.
^ Dan Harrington and Bill Robertie (2005). Harrington on Hold'em: Expert Strategy For No-Limit Tournaments; Volume II: The Endgame. Two Plus Two Publications. ISBN 1880685353.

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