You may want to get your hands on S Wongs tourney BJ book. I don't have it, but have heard that it will give you the low down on proper play techniques.
Basically from my own experience, I try to get within a stones throw of first spot, then on the last hand try to jump to first, with a bet that will put me there, and not lose my second place finish otherwise. If this is not possible, I will simply try to stay ahead of #3. It depends on where you find yourself in the last momments of play. Watch a NASCAR race and see how wreckless that last lap gets and you'll get the picture! ;>
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.