I know for sure the eye thing is a sure fire way- Given! I know there is a guy at my gym who always steals glances at me, so I approached him a couple of days ago. I saw he was doing some crunches on a ball and I purposely sat right next to him on the mats doing some stretches, while I was stretching I noticed him stealing glances every few seconds when he thought I wasn't looking. When I looked at his direction he would look away. I even took it one step further and tapped him on the shoulder and asked polity if he was using this foam roller right next to him. and the guy couldn't even look at me in the eye as all I got was a nod with a flustered face.