In Blackjack, you should consider doubling down when you have a strong hand, such as a total of 10 or 11, as you have a good chance of drawing a 10-point card to reach 20 or 21. It's also a good option with a "soft" hand (like Ace + 5, Ace + 6, or Ace + 7) when the dealer has a weak upcard (2–6), since they’re more likely to bust. Doubling down is a strategic move when the dealer is showing a weak card, and you can capitalize on their potential disadvantage. However, you should avoid doubling down if you have a hard 12–16 or if the dealer has a strong upcard (7–Ace), as the risk of busting or the dealer’s potential strong hand outweighs the reward.