The machine accepts any credit bets. It then randomly determines the position of the symbols on the video display to produce an outcome, which is completely unrelated to the previous game's outcome. If the machine determines a win, credits are paid.
No, there is no way to predict when a slot machine is going to hit a jackpot or to determine which machine is going to be lucky. Slot machines are programmed to use a random number generator (RNG) to determine the outcome of each spin, and the RNG generates random and unpredictable results.