Blackjack - Strategy

As in all casino games, the house generally has a statistical advantage over the players that will play itself out in the long run. But because blackjack, unlike other games, has an element of player choice, players can actually reduce the casino advantage to a small percentage by playing what is known as basic strategy. This strategy determines when to hit and when to stand, and also determines when doubling down or splitting is the correct action. Basic strategy is based on the player's point total and the dealer's visible card. There are slight variations in basic strategy depending on the exact house rules and the number of decks used. Under the most favorable conditions (single deck, downtown Las Vegas rules), the house advantage over a basic strategy player can be as low as 0.16%. Indeed, casinos offering special rules like surrender and double-after-split may actually be offering a positive expectation to basic strategy players; they are counting on players making mistakes to make money.

It is important to remember, however, that the small house edge only applies over long period of play. This is because most of the time a player has cards, he will always be in a position where he is most likely to lose. Doubling and splitting when in a profitable position are absolutely essential to maximising returns. Without doubling or splitting at the correct times, the house edge increases dramatically.

The following rules are beneficial to the player:

1. Doubles are permitted on any two-card hand except a blackjack. This allows the player to choose to double when he is most likely to win, and not double when he is not likely to win.
   
2. Doubles are permitted after splitting. This allows a player to potentially get many bets out in a situation that he is likely to win, such as against a dealer card of 6, the worst card the dealer can have.
   
3. Early surrender; the ability to forfeit half your wager against a face or ace before the dealer checks for blackjack. This is beneficial because some hands a player has are so unlikely to win that its better to just surrender half the bet.
   
4. Normal (aka "late") surrender.
   
5. Resplitting Aces. Obviously this avoids a player getting a miserable total of 12.
   
6. Drawing more than one card against a split Ace. This allows a player to draw a weak soft total if the dealers is showing a high card.
   
7. Five or more cards with the total still no more than 21 as an automatic win (a "Charlie"). This is not a commonly seen rule.

The following rules are detrimental to the player and a game that uses these rules should be avoided at all costs:

1. Less than 3:2 payout on blackjacks (6:5 and even 1:1 payouts have become common, especially in single-deck games, in Las Vegas since about 2003). This is the worst rule for the player, the house edge is increased over eight fold, a player loses money over eight times more quickly at this game.
   
2. Player losing ties. This is just as bad as having a low blackjack pay out, since a tie will occur almost 8% of the time. A player will lose money up to and over twenty times faster at this game. Note that even in cases where the casino shows both dealer cards face up, allowing the players to see the dealer's full hand, the rule is more detrimental to the player.

The following rules increase the house edge, but only slightly:

1. Dealer hits on soft seventeen (ace, six). Makes the house more likely to land a higher total.
   
2. Splitting a maximum of once (to two hands). This can nullify the effect of splitting altogether since a player could end up with the exact hand they started with. The effect is very very little, but when this rule is applied eights should be split less often against tens or aces).
   
3. Double down restricted to certain totals, such as 9-11 or 10,11. The player cannot hit on soft totals that he may have an advantage at.
   
4. Aces may not be resplit.
   
5. No-Peek (European) blackjack—player loses splits and doubles to a dealer blackjack, as opposed to only losing original bets. When playing this game a player splits and doubles against a dealer ten and ace less often.
   

From Wikipedia's