One of the most important things to consider when playing on slot machines (or slots) is the parentage payout on different machines. These actually vary enormously, and whilst the most generous slots will pay out up to 98% of the money staked, others will pay out only 80% or so and sometimes even less.
This average payout percentage is not a random factor. It is very carefully determined and accurately controlled by computers and it is based on a combination of the frequency of wins and the amount of money that is paid out on a win. The computers that control slots in live casinos (and online casinos) are carefully regulated and guarded and nowadays they are far too secure for players to tamper with, though of course this was not always the case.
The only strategy that is worthwhile is to play on machines that have a high payout. These are generally referred to as loose machines; however identifying them is not an easy matter. Although casinos are forced by law to show the payouts on their machines, these are average payouts and not the payout on each individual machine. In the whole bank of available machines some will be loose and some will be the opposite. Thus regular players attempt to identify loose machines and if they are successful in doing so then they jealously guard them; sometimes they work in teams so that the machine is kept in play by team members.
Many people believe that the best slot machine strategy is to play on machines with a high payout (say progressive slots) that have not paid out for some time. Their reasoning is that because a machine has not paid out for some time a payout is due, as in the probability of a payout is higher that if the machine had recently paid out. As each spin is an individual event, this kind of thinking is flawed and is what is known as the gamblers folly. The probability of payout cannot change as a function of previous payouts.
One way in which machines with high jackpots can be exploited is by calculating expected value. In certain circumstances the jackpot can be sufficiently large to give each bet a positive expected value which means that if you could take over exclusive use of the machine and you had a huge (infinite) bankroll, you could guarantee making a profit, but those are big “ifs”.