The most important thing to know about blackjack is the basic strategy. This strategy is simply the best way to play every possible situation, without any knowledge of the distribution of the rest of the cards in the deck. Following is the basic strategy for four of more decks when the dealer stands on soft 17. Links are also provided to more basic strategy charts for other rules. However the most common game is the multiple deck game (4 or more decks) where the dealer stands on soft 17. If you only memorize one table I would suggest the one below. It can be played effectively under any rules.
To use the basic strategy look up your hand along the left vertical edge and the dealer’s up card along the top. In both cases an A stands for ace. From top to bottom are the hard totals, soft totals, and splittable hands. Rule variations can have an effect on some borderline situations. The most flexible rules are the number of decks, whether the dealer hits or stands on a soft 17, and whether doubling is allowed after splitting.