Casinos rake in millions from players’ mistakes at the blackjack tables. But what are the most common blackjack mistakes you will see when you sit down at a casino blackjack table? The following rankings are qualitatively based on expected loss, frequency of occurrence, and frequency of the error.

The correct decisions are based on a standard 6 or 8 deck game, dealer stands on soft 17, and hands may be split to up to 3 times for a total of 4 hands. (Aces may only be split once.)

• 10) Hitting 4/4 when Dealer shows 6
  
  Expected Loss vs. Splitting: $4.20 for every $100 bet
  A player with two fours should split the hand against a dealer’s 6. When the dealer shows a 6, you generally want to play as many hands as possible because the dealer is likely to bust.


• 9) Hitting 2/2 when Dealer shows 7
  
  Expected Loss vs. Splitting: $9.68 for every $100 bet
  Twos are surprisingly good cards to start with as a player. And it is likely the dealer has a “stiff hand” or a 17. So split that 2/2 and make some money.


• 8) Doubling 11 when Dealer shows Ace
  
  Expected Loss vs. Hitting: $2.49 for every $100 bet
  When the dealer has an Ace, you have to be careful. Hit your 11. You’ll be better off, and you won’t have to sweat it out. (But be aware that doubling is actually the correct play when the dealer hits on soft 17.)


• 7) Standing on a 12 when Dealer shows 2
  
  Expected Loss vs. Hitting: $3.83 for every $100 bet
  This decision is not intuitive. When the dealer has a 2, you are inclined to wait for him to bust, but a 2, and even a 3, could be a dangerous up card for the player. So hit on a 12 when the dealer has a 2 or a 3.


• 6) Hitting 11 when Dealer shows Ten
  
  Expected Loss vs. Doubling: $5.94 for every $100 bet
  One of the benefits of playing blackjack is that you can choose when to put more money on the table. When you have an 11 and the dealer doesn’t, go for it. You can expect to make about $18 for every $100 you bet, while hitting will only earn you about $12.


• 5) Standing on Soft 18 when Dealer shows 9
  
  Expected Loss vs. Hitting: $8.37 for every $100 bet
  You see this all the time. Nobody wants to ruin an 18. The problem is that when a dealer has a 9, an 18 might not cut it. If the hidden card is a Ten or an Ace (which it is, about 38% of the time), then you’ve lost. So give yourself a chance, and hit it!


• 4) Standing on Soft 18 when Dealer shows 6
  
  Expected Loss vs. Doubling: $10.13 for every $100 bet
  Take a chance and double. Even if you get a card you don’t want (like a 5), there is still a good chance (about 42%) that the dealer will bust.


• 3) Standing on 16 when Dealer shows Ace
  
  Expected Loss vs. Hitting: $14.94 for every $100 bet
  Standing on 16 when the dealer has Ten is not nearly as bad as when the dealer has an Ace. There is a good chance you are going to bust, but you have to give yourself a shot to win or push. Otherwise you have to count on the dealer busting with an Ace.


• 2) Splitting Tens when Dealer shows 6
  
  Expected Loss vs. Standing: $52.58 for every $100 bet
  This is painful to watch. Please don’t do it. You will still generally make money when you split (less than $18), but you can expect to make over $70 by doing nothing. So don’t be cute. Always stand on a hard 17 or greater.


• 1) Taking Insurance or Even Money
  
  Expected Loss: $7.77 for every $100 insurance bet
  You’ll be paying a premium to buy insurance. Don’t do it! And besides, you’re playing blackjack because you like to gamble. So go on and gamble. Almost 7 out of ten times the dealer will not have blackjack.