Celarent Darii (1561999)
writes "The probability of winning at Rock-Paper-Scissors is about 1 in 3. However, people do not play entirely randomly, a study has revealed. People tend to follow hidden patterns that can be used to win more games. A short article on the BBC gives hints on the strategies to be used to get a competitive advantage with your Rock-Scissors-Paper nemesis."
Remember, these strategies are for use against people, not robots