“The only way to beat Roulette is to steal chips from the table.” /Einstein/
This quote of Albert Einstein is true. There are no 100% safe strategies in casinos. If there were, then everyone would be playing in casinos and, to be honest, no casinos could exist. To win in a casino you either have to be extremely lucky or know the strategies that have the best chances of winning. There are no such strategies in slot machines, but there are in roulette. For example, everyone probably knows the Black and Red Strategy where the Martingale theory is used. This is the most popular, but not the only strategy that can be used to win the casino.