Only one card for split Aces: a single new card is added to each Ace and the turn ends. They are thus regarded as 11-point cards. No other denomination is subject to this process.
Multiple splits: If a player splits 2 cards and receives a third card of identical value, the hand can be split again, resulting in 3 hands. However, some casinos only allow a single split of the first 2 cards.
Early surrender: Player has the option to surrender before dealer checks for Blackjack.
Late surrender: Player has the option to surrender after dealer checks for Blackjack.
Double-down restrictions: Double-down may only be allowed on certain combinations of cards (usually totaling 9, 10 or 11).
Double-down after split: Double-down may not be allowed after splitting cards. The split hands are played normally otherwise.
Split any tens: Players may split any 2 cards which are both worth 10 points, such as a Jack and Queen. This rule is rarely used, since 20 is a very strong hand which is unlikely to be split.
European No-Hole-Card Rule: the dealer receives only one card, dealt face-up, and does not receive a second card (and thus does not check for blackjack) until players have acted. This means players lose not only their original bet, but also any additional money invested from splitting and doubling down. A game that has no-hole-card doesn't necessarily mean the player will lose additional bets as well as original bets. In some Australian casinos for example, a player beaten by a dealer blackjack may keep all split and double bets and lose only the original bet, thus the game plays the same as it would if there were a hole card.
Each blackjack variation has its own set of rules, strategies and odds. It is advised to take a look at the rules of the specific variation before playing. Many countries have legal acts and laws, which determine how a casino game of Blackjack must be played.