Rules v Strategy
Joan, are you asking about different game rules or different strategy. Rob's answer talks about strategy, but I have found that the rules are sometimes different as well. In my area, it is VERY common for blackjacks to pay 2 to 1 in tournaments. Also, they never allow surrender (even when the casino has it on their regular game). This may be different for other locations.
One interesting thing about the 2 to 1 BJ rule is that they will let you take even money or insurance if you have a BJ and the dealer has a face up. Obviously, you should never take even money in that situation, but I find that most players will do exactly that. The other key difference is that dealers are prohibited from giving advice (along with spectators), which is nice. So in the even money / insurance situation, the dealer will usually ask if anyone wants insurance, without mentioning even money. However, if a player asks for even money then the dealer is not supposed to correct them.