Hold 'em is normally played using small and big blind bets forced bets by two players. Antes (forced contributions by all players) may be used in addition to blinds, particularly in later stages of tournament play. A dealer button is used to represent the player in the dealer position; the dealer button rotates clockwise after each hand, changing the position of the dealer and blinds. The small blind is posted by the player to the left of the dealer and is usually equal to half of the big blind. The big blind, posted by the player to the left of the small blind, is equal to the minimum bet. In tournament poker, the blind/ante structure periodically increases as the tournament progresses. (In some cases, the small blind is some other fraction of a small bet; e.g., $10 is a common small blind when the big blind is $15, and still other tables may use two equal blinds. The double-blind structure described above is a commonly used and more recent adoption.)
When only two players remain, special 'head-to-head' or 'heads up' rules are enforced and the blinds are posted differently. In this case, the person with the dealer button posts the small blind, while his/her opponent places the big blind. The dealer acts first before the flop. After the flop, the dealer acts last and continues to do so for the remainder of the hand.
The three most common variations of hold 'em are limit hold 'em, no-limit hold 'em and pot-limit hold 'em. Limit hold 'em has historically been the most popular form of hold 'em found in casino live action games in the United States. In limit hold 'em, bets and raises during the first two rounds of betting (pre-flop and flop) must be equal to the big blind; this amount is called the small bet. In the next two rounds of betting (turn and river), bets and raises must be equal to twice the big blind; this amount is called the big bet. No-limit hold 'em is the form most commonly found in televised tournament poker and is the game played in the main event of the World Series of Poker. In no-limit hold 'em, players may bet or raise any amount over the minimum raise up to all of the chips the player has at the table (called an all-in bet). The minimum raise is equal to the size of the previous bet or raise. If someone wishes to re-raise, they must raise at least the amount of the previous raise. For example, if the big blind is $2 and there is a raise of $6 to a total of $8, a re-raise must be at least $6 more for a total of $14. If a raise or re-raise is all-in and does not equal the size of the previous raise, the initial raiser cannot re-raise again. This only matters of course if there were a call before the re-raise. In pot-limit hold 'em, the maximum raise is the current size of the pot (including the amount needed to call).
Most casinos that offer hold 'em also allow the player to the left of the big blind to post an optional live straddle, usually double the amount of the big blind, which then acts as the big blind. No-limit games may also allow multiple re-straddles, in any amount that would be a legal raise.