There can be opportunities during a game of blackjack where the conditions are favorable enough for you to increase your bet, which will in turn payout more if you win.  One way to do this is by “doubling down” on your first two cards by placing an additional bet on your hand which matches your original bet.  When you do this, however, you agree to take only one more card from the dealer, no more.

Obviously, doubling your bet should only be done when the conditions are very favorable for you to win.  In other words, when your hand is strong and the dealer’s hand is weak.  A good example of this is if you have a hand that totals 10 or 11, and the dealer’s hand is 5 or 6.  In this situation a card with a value of 10 will give you a total of 20 or 21, which is almost always a winner.  Even a 9-card will give you a hand that has a lot of potential against a dealer’s weak hand.

Basic strategy recommends that you always double down when your hand totals 11, regardless of the dealer’s face-up card.  It also recommends that you double down on a hand with a value of 10, unless the dealer is showing a face card of 10 or ace.  In this instance, hitting would give you a better chance to beat the dealer’s possible 20 or 21.  If you should get a third card that is a 2 or 3, then you will have the option to take a fourth card, which would not be available if you double down.

When playing single-deck games, you should only double down on a hard 9 when the dealer is showing a 2 through 6, and in multiple deck games when the dealer is showing a 3 through 6.  If your hand totals 12 through 16, then you should not double down no matter what the dealer is showing.

When playing with an ace, or soft-hand, doubling down makes sense only if the dealer is showing a weak hand.  In single deck games, if you have an ace paired with a 2 through 5, and the dealer is showing a 4, 5, or 6, then you should consider doubling down.  If you have an ace and a 6, then you might want to double down when the dealer is showing a 2 through 6.  Also, if you have an ace/7 pair, then you should double down only if the dealer is showing a 3, 4, 5, or 6.

When playing multiple deck games, if you have an ace/2 or ace/3 combination, then you should only consider doubling down if the dealer is showing a 5 or 6.  If you have an ace/4 or ace/5, then double down if the dealer is showing a 4, 5, or 6.  When holding an ace and a six and the dealer is showing a 3 through 6, then you can consider to double down.  As in the single-deck games, you can double down on an ace/7 pair when the dealer is showing a 3, 4, 5, or 6.      

While most casinos will allow players to double down, some limit their players to double down on only a 10 or 11, and others will not allow a double down on cards that have been split.  Overall, the fewer restrictions that there are on double down rules, the greater advantage there is for the player.

Another strategy that is used by the player as a method to offset the casino advantage is called splitting.  As a player, you can split any two identical cards in your original hand, such as two 8’s.  If you choose to split, then each of the cards is separated, face up.  Then simply place a bet equal to your original bet in front of your new hand of cards.  Each hand will then be played independently by either hitting or standing.  You can win, lose, or bust on either or both hands.  This increases your potential for making more money, but, remember, that it also increases the likelihood to lose more.

You may be tempted to automatically split your “pairs” into two hands; however, this strategy will only work to your advantage on certain pairs, and is also dependent on the dealers face up card.  It is a good rule of thumb for you to almost never split 5’s or 10’s.  If you split 5’s then you leave yourself open to ending up with a value of 15 on each hand and a higher probability of busting on the third card.  Keeping the 5’s will give you a good starting point of a solid 10.  This will give you a better chance of ending up with an 18 or higher after the second card, thus increasing the likelihood to beat the dealer. 

As for splitting 10’s, I can’t think of any hand where this could be to your advantage.  You already have a hand with a value of 20, which is almost always a winner.  Once you split 10’s, the chances of you getting an ace on either or both hands are pretty low.  Besides, in most casinos, if you split either 10’s or aces and end up with a blackjack on one of your splits, then you only get paid even money.  You won’t get paid the higher payout for a natural blackjack, which is only paid on the first two cards.

Basic strategy recommends that you always split 8’s because together you have a hand with a sixteen value, which is rarely a winning hand.  By splitting these cards you have a good chance of getting a solid 18 on either or both hands, thus changing a weak hand into a strong hand.  Basic strategy also recommends that you split aces, no matter what the dealer is showing.  Since there is a higher concentration of cards with a value of 10 in the deck, you have a really good chance of ending up with a couple of hands worth 21.

Splitting pairs with face-value cards are largely dependent on the dealer’s cards and whether the game is being played with a single-deck or multiple decks of cards.  The following chart identifies the moves that basic strategy recommends on splitting pairs.