Deuce to Seven Single Draw is a variation of lowball poker that's become popular again over the last few years. It differs from games like Hold'em, because it's the lowest hand that wins the pot.
The easiest method of determining who has the lowest hand is to start with a player's worst card (their highest ranking card) and work backwards. One player holds 9,8,6,3,2 and another has 9,8,6,4,2 and both have no possible flushes, the first hand is declared the winner as the 3 is lower than the 4.
The best possible hand is 7,5,4,3,2 avoiding a flush. If both players involved in a showdown has a pair (this is rare) then the player with the lowest pair would win the hand. It's also worth noting that A,2,3,4,5 is not a straight as the ace is high.
In 2-7 Single Draw, a marker called 'the button' or 'the dealer button' indicates which player is the nominal dealer for the current game. Like all draw games, 2-7 is played with blinds which are posted by the player on the left of the dealer (known as the small blind), and the player second-left from the dealer (the big blind). Once this is done each player is dealt five cards face down.
In the first round of betting, the player sitting to the left of the big blind has the option to fold, call or raise. Each player may do the same and the action continues around to the blinds (the blinds may raise, even if there is no bet in front of them as their blinds, or bets, are 'live').
After this first round the draw take place. Each player selects which cards he wishes to discard (if any) by clicking on them. He can discard all his cards if he wishes. Clicking once chooses that card to be discarded, clicking twice cancels this decision. Discarded cards are then replaced by new cards.
This continues for each player in a clockwise direction around the table. When it is your turn you press the button which confirms you wish to discard the cards selected. Choosing to 'stand pat' means you are happy with the five cards you have been dealt and do not wish to change any.
The next round of betting starts with the player to the left of the dealer who has not yet folded and the action continues clockwise, until all betting is concluded Now comes the showdown. The player with the best five card 2-7 low hand after the final round of betting is awarded the pot. If two players have the same winning hand then the pot is split evenly between them (note that suits make no difference in this case).
In draw games, it is possible for more cards to be needed than are remaining in the deck. In this case, the cards are reshuffled, and play continues using the new deck.
The minimum bet in No Limit 2-7 Single Draw is the same as the size of the big blind, but players can always bet as much more as they want, up to all of their chips.
Minimum raise: In No Limit 2-7 Single Draw, the raise amount must be at least as much as the previous bet or raise in the same round. Maximum raise: The size of your stack (your chips on the table).
In No Limit 2-7 Single Draw, there is no 'cap' on the number of raises allowed.
Don't forget that PokerStars also offers Deuce to Seven Triple Draw.