The poker card game is one of the staples of western movies (especially older ones, made in the 70's and earlier.) Almost invariably it will be depicted as straight poker, meaning that each player is dealt five face-down cards, from which they can swap any number of cards with new ones, after which there is a round of betting, with possible raises. When non-folding players have all bet the same amount, cards are revealed and the winner takes the pot.
The choice of this poker variant is probably realistic, as it's one of the oldest variants, and probably the most common in the United States in the 19th century. Variants that are today more popular, like Texas Hold'em, didn't exist back in the 1800's.
There are many clichés that you can see in lots of these movies, especially older ones. Many of them feel quite strange.
One of the most common ones is the player who runs out of money and can't match a bet. Often he will then search for valuables to bet, or ask for a loan, or something similar. The implication being that if he can't match the bet, he just loses by default.
This seems highly strange. I have no idea what the poker betting structure was in those times, but it feels highly, highly unfair, to the point of making the whole game moot. The richest player would always win by making an all-in every single time. Since no other player could match his bet, he would always win by default. Which would make absolutely no sense.
I remember one movie in particular, where a woman was playing poker against a group of men, and she ran out of money and couldn't match a bet. It ended up with all the players going to a bank, where she asked the bank's owner for a loan.
Maybe this was solved back in those days with betting limits (ie. you can't bet more than a certain amount.) However, I don't remember ever seeing this mentioned or depicted in any of these movies.
The modern solution to this problem is the side pot mechanic: If you make an all-in, and somebody then raises to even more than that, the extra money goes to a side pot, where any remaining players will continue betting any amounts above the main pot bet. (On showdown, or if all other players fold, the side pot goes to the winner among those other players, after which a showdown of the main pot, now including this original all-in player, will ensue.) This means that you can always participate, even if you have one single coin left. (Your current amount of money simply limits how much you can win at most, which is that amount times the number of players, assuming all match your bet.)
As said, I have no idea how this problem was resolved back in those times. The cliché so popular in movies (ie. it's not solved at all) seems completely nonsensical, though. It might make for drama or comedy, but it's still nonsensical.
Another cliché, perhaps even a more common one, is the crucial showdown, where the bad (or at least antagonistic, often unpleasant) guy shows a very strong hand, like a straight or a full house, and without waiting for the protagonist to show his hand goes to grab the pot. Of course only to be stopped by the protagonist showing even a stronger hand, like four of a kind. The antagonist is shamed with his hands around the money, which he then can't take.
Very commonly this antagonist is depicted as a very experienced and ruthless poker player. Which raises the question of which poker player would just go to grab the pot without waiting to see his opponent's hand? This feels a bit unrealistic, and artificially played for drama or comedy.
This one is often not unrealistic, especially if we are talking about a 19th century decrepit saloon in the middle of nowhere, or a friendly game at someone's home, or something along those lines, because it probably happens a lot in real life as well (probably because it's so common in movies and people will imitate them!) but another cliché is the player who does a "I call your hundred... and raise 500!" This may be ok in casual informal play, but especially in more official tournament play, and in groups with more formal rules, that's an improper way of announcing your action. This especially if it's accompanied by the player first throwing the 100 into the pot and then 500 more (which is likewise very common in these movies.)
In fact, in most tournaments, with strict rules, if you say "I call", then that's it: You have called. You can't then raise. It doesn't matter if you amend those words with "and" anything. The proper way to raise, if you say it out loud, is to say directly "I raise". And first putting forward some coins and then more is outright forbidden. You have to make the entire bet at once, not in parts.
