Books have been set forth on this topic, and the debates and discourse about where the "hot" slots are located in the casino are still ongoing – more than sixty years after slot machine games were 1st added to the gaming floor in gambling houses.
The classic rule is that the best slot machines were placed just inside the main entrance of the casino; so that potential gamblers passing by would be able to see actual jackpot winners and be drawn to come into the casino … play. Our estimation is that this is no longer true.
Practically all of the mega casinos nowadays are immense complexes and it is not possible to see inside from the sidewalk, so there is no longer a reason to position the ‘loose’ slots near any of the doors.
Another traditional rule is that loose slot games are put on the major aisles inside the casinos, again so that more potential gamblers could see winning jackpots and be influenced to play. Notably though, we find that this also is no longer a universal rule.
What casinos found over the years is that people walking down the busy aisles were frequently on the way to somewhere else. If they played the slots at all, they would simply put in their loose change because they happened to be walking by. Win or lose, they would very often not stop to keep playing. And the very last thing a casino wants is for someone to win a jackpot by playing only a few coins and then not stay to put it all back in!
Today, casinos are constantly changing their philosophy about where to place the loose slot machines.