Rock-paper-scissors is this sort of game that seems to be completely random. But group of Chinese scientists ran this experiment with 360 students playing the game for two hours. There are two rules that you can follow and have better chances to win the game, assuming that your game partner does not follow the same strategy. Click on the spoiler button to see these rules.
Rule #1: If you lose in one round, then on the next round change to the shape that you should have in order to win this last round. For example, you bring the rock, and your partner brings the paper and you lose. On the next turn bring the scissors.
Rule #1: If you win the round, then on the next round switch to the shape that your partner had. Say you bring the rock and your mate brings the scissors and you win. On the next round bring the scissors.
Or just enjoy watching the following video which explains them in details...