As far as looking at past games is concerned... one can "set up" someone they suspect of using their past history to help them win games. You can make it look like an old predictable game, but drive them crazy tring to figure out whats wrong, and by the time they do, you have beaten them :)
But by playing predictably unpredictable, no one will know for sure what you are up to in a particular game until it is too late.