To the novice or even the intermediate player, the number of decks in a blackjack game should not make a difference in your style of play. As long as you stick to your basic strategy, you will be able to get close to the lowest house edge without worrying about a contingency plan for every possible game variety. However, there are some variations that you should take note of before you sit down at a blackjack table.
Commonly, a casino will use four to six decks in a standard game of blackjack, though the game was originally played with one or possibly two decks. These decks are shuffled together – usually using an automatic shuffler – cut by the dealer, and then placed into a ‘shoe’ from which the cards will be dealt to the patrons and the dealer. The dealer will use this current shoe of cards until a set point is reached, at which point the cards will be reshuffled. Six decks results in a total of 312 cards, making card counting significantly more difficult than in games with only one or two decks (discussed further in How to Become a Professional Blackjack Player).
Interestingly enough, many casinos in Las Vegas and Arizona are re-introducing a single-deck blackjack game. While on the surface this change may sound like a boon to card players everywhere – as games played with one deck offer more opportunities to double down – it comes with several caveats. Many of these tables only pay 6-5 on blackjack instead of the usual 3-2, significantly increasing the house edge. These tables may also allow the dealer to hit on a soft 17 (an ace and a six), which further raises the casino’s edge over the player. In short, you should avoid single-deck tables at all costs since they incorporate rule changes that are detrimental to the player.