Craps: Despite the fact that most craps tables have a throng of people crowding to get any piece of the table where they can bet from, and that most of the time the players are betting on someone else's roll, our hero will always be at the head of the table and will always be the shooter for the length of the sequence.
Roulette: Our hero never bets groups of numbers. He only bets a single number or on red or black. He never bets on odd/even. He almost always puts all his chips down on a single spin. This is especially true if he is playing red/black.
Blackjack: All movie and television heroes can count cards. Not only that, but this ability allows them to win instantly and consistently, despite the fact that real card counting may take hours of meticulous concentration before paying off. The hero will usually get escorted or chased away by casino security rather than getting up of his own accord.
Poker: At some point during the sequence, our hero, whether bluffing or holding the nuts, will go all-in for his entire stack. He is also likely to say "I call your (x amount) and raise you (y amount)" even though calling and raising are two separate actions and to try to do both is a clearly illegal string bet.
Slot Machines: Playing slot machines is not heroic. Our hero will play one coin by accident (he happens to have an extra quarter while waiting for a friend, for example). This coin will win him or her a huge jackpot, despite that most slot machines will not pay off a major jackpot unless you play at least five coins. If a secondary character has played a machine for hours to no avail, the very next person who puts a coin in the machine will win a huge jackpot.
Baccarat: Our hero will appear to be a very skilled baccarat player, despite the fact that there is not an iota of skill involved in baccarat.
Sports Betting: Sports betting is for losers. If our hero bets on sports, it's only to show that he has a gambling problem. Anyone else who bets on sports will usually lose, although a final bet may become a miracle win to save the bettor from total disaster, at least temporarily.