One of my best friends and I would travel to the local casino some years back from time to time. Wasn't a very fun casino but it was about as good as we could get for those times as gambling was very restricted back then. He was a big fan of playing slots and always seemed to have some sort of strategy. He would look for players who were sitting at a machine for a long period of time and then play them. There were a couple other things he did that he called "strategy" but I can't remember what they were.
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This is a well-known strategy (at least in my country 10 years ago, maybe now something has changed in the algorithms). It is based on the fact that when the slot machine was "fed" it must "give". Therefore, some operators of gambling clubs watched slot machines and when they saw that a visitor lost a lot of money on one of the machines, they themselves began to play on it, guessing the moment when it should "give".
And unfortunately that is a strategy that does not work, slot machines are not programmed to give some money after a certain amount of money has been played in the machine, it is random, and each game you play there is an independent event, and as such what happened in the past has no relevance to what will happen in the future with that machine.
There are games in which the past matters, one example of this is blackjack, in which if you take an Ace out of the multiple decks of cards used to play the game then the number of Aces on the decks went down by one, this is why something like card counting works, but I am not aware of anything like that being possible with slot machines.
