In European blackjack and in many online casinos the dealer does not check for a blackjack after dealing the cards. This is referred to as the 'no-peek' rule, because the dealer doesn't peek to see if he has a blackjack. In this case, after the players have played their hands, if the dealer does have a blackjack, then the player loses the full amount bet, including the additional bet if the player doubled or split.

Insurance

Do not take insurance, even if you have a blackjack. Card counters can get away with making smart insurance bets when the deck is rich in tens but the non-counting player should always decline it.

Surrender

Sometimes in a 6 or 8 deck game the player has the option to surrender. To be specific the player may forfeit half their bet to be excused from playing out their hand. Obviously this option should only be taken in the worst hands when the net return is less than 50%. In late surrender (the only kind I have ever seen) the player may only opt to surrender after the dealer checks for a blackjack.

Five Card Charlie

A 'five card Charlie' is an automatic winner on any five card hand that has not busted. This rule does not apply after splitting or if the dealer has a blackjack.