On Reddit, a wonderful thread where redditors detail their favorite "mind tricks."
Here's a smattering:
When I walk through large crowds of people, to avoid walking into anyone, I simply stare at my destination. I look no one in the eyes. People actually will watch your eyes and they avoid the direction you are going. If I look into people's eyes as we are walking into each other, we are sure to collide. You have to let people know where you intend to go with your eyes. It always works for me, try it! (Poo_Smudge)
See full list at http://boingboing.net/2011/12/04/mind-tricks-to-try-and-use.html