Slot machines are supposed to be random, but they are not truly random. A program runs on the machine making sure that they pay out at a certain rate. You can't really predict the outcome of a slots game. But, there are strategies to win; since a slot machine is supposed to pay out after so many pulls then if you stay on one machine long enough it will pay, but what it pays is random and you cannot be sure of a jackpot. Another other method is to go to a casino with "loose" slots--a higher payout rate. Usually the management of the casino knows the payout rate. Some casinos even advertise that they have "loose" slots in the hope that you will come, gamble, and still loose a lot of money.
Look at how beautiful casinos are, how large they are, and how they have no problem of offering free drinks to gamblers. Do you think they do this because they are kind? Casinos are a big money making investment, and one of their best sources of revenue are the slot machines.
So if you play the slots then set aside how much money you want to play with before hand, and stop at that point. You also have to have the attitude that you are doing this for fun, and that you will most likely loose all your money. That's why I prefer video games, you get a longer play and you don't have to worry if you are going to win or not. Finally by playing the slots you are giving the casinos the money they need to pay off that massive grand jackpot, and still make a profit.