BlackJack
Player's Choice - Doubling Down
Among the more profitable player options available is the choice to "double down". This can only be done with a two card hand, before another card has been drawn. Doubling down allows you to double your bet and receive one, and only one, additional card to the hand. A good example of a doubling opportunity is when you hold a total of 11, say a (6,5) against a dealer's upcard of 5. In this case, you have a good chance of winning the hand by drawing one additional card, so you might as well increase your bet in this advantageous situation.
Players are allowed to double down for any amount up to the original bet amount, so you could double down "for less" if you wanted. Just remember that you do give up something for being allowed to increase your bet: the ability to draw more than one additional card. If the correct play is to double down, you should always double for the full amount if possible.
Double Down - a player may place an additional bet the same as his original wager, if they hold any two cards with a total of 9,10,11 and then shall draw only one card.