In high school I actually had a friend teach me this in a humorous way. In football we did sprints (the kind where you physically run) at the end. He said -- half ass the sprints. Then on the last sprint, run as fast as you can, you'll have more energy left, and when they see you running fastest you'll get all the credit. He was doing it as a joke, but lo and behold he out runs everyone on the last sprint by a lot, and the coach specifically pulls him aside as an example of how everyone else should carry themselves.

He's one of my favorite pranksters. But needless to say, the football team was not very good.