Many first time blackjack players do not understand the concept of doubling down. The double down is a crucial strategic weapon in the arsenal of any discerning blackjack player, as it allows you to double your bet when you may have a bigger edge.
For example, say you have 11 after two cards, and the dealer is showing a 6. You know that a face card would give you 21, and you also know for sure the dealer must take at least one more card, which could bust them. So, you simply put a second bet next to your original bet, and you are given ONE (only one) more card, and your final hand is whatever the total of those three cards are.