In reality, the hacked machine is not only a plausible scam, it's actually happened on multiple occasions. In the early nineties, dozens of slot machines were reprogrammed by Ronald Dale Harris, an employee of the Nevada Gaming Commission whose job it was to make sure such machines were fair.

The best way to increase your odds of winning on a slot machine is to not play. The probability of winning on any spin of the game is set by the game's program, and nothing you can do will affect that. The game is always set so that in the long run the machine will pay out less than what is wagered.