The last time I went back to Oklahoma, I played slots at a Cherokee casino between Tulsa and Catoosa. You would enter bills and when you cashed out you got a cash voucher you had to redeem at a cage. Anyway went in with my parents on a Saturday night and right before we left I noticed a strange occurence on the slot I was playing. When I entered $20 into the bill acceptor that at some point before I lost all of the $20 I would usually get a big win to double up (i.e. $40), but if I continued to play I would eventually lose all the money. So I employed a strategy of once I doubled my winnings I would immediately cash out and get a cash voucher, and then put another $20 bill in. I did this 3 consecutives times and had 3 cash vouchers for approx $120 to cash in. I made a mental note of the slot machine in my head and left thinking the next time I come back to Oklahoma I would try the same stragegy on this slot machine.
My flight was the next morning (Sunday) leaving from Tulsa back to Salt Lake City. My parents dropped me off and left to go back home. They do not have a cell phone and its a hour drive from Tulsa where they live. When I got inside the airport I found out my flight that morning was cancelled, but I was able to get on a flight later than afternoon. Knowing I had no way to get a hold of my parents to come back to the airport, I rented a car and went back to the casino. I had $300 in 15 $20 bills so I went back to that slot machine and employed this strategy of putting a $20 bill and if I ever doubled up to cash out and get a cash voucher and play the strategy over and over. This strategy worked every time and in 2 hours I had increased my $300 to $900. I did have alot of vouchers though that I had to cash in so I spread them out cashing them in at the 4 different cages they had through out the casino. I knew I would never be able to describe the slot machine to my parents so I took a picture of the slot machine and the layout using my cell phone and sent it to my parents from the airport. My dad went back later that night and said the machine had a sign saying out of order. I'm sure the cash vouchers somehow identified the slot in question. So at least once this strategy worked for me, where it appeared the slot was loose to allowing you to double your money after you entered your money but then would go on a cold streak after that. I don't know who oversees the Indian gaming in Oklahoma but I doubt this strategy would work in states where the slots are more closely regulated.