so I was reading some post about body language and one of the things that is supposed to indicate interest is big pupils. People have been shown to unconsciously rate faces with larger pupils as friendlier. It's one of the reasons why candlelight is romantic.
Well I was reminded of that article when this girl showed me how to enlarge and shrink pupils at will. I don't mean for anyone to attempt to use this tric to subconsciously influence anyone (you'd probably look a bit idiotic, plus you can't see much when your doing it) but its a fun trick... at the very least you can get someone to look deep into your eyes

If nothing else you can freak people out. This works better if you have light colored eyes.
K here is what you do...go up to a mirror, then relax you b ody. Lose focus in your eyes, force them to be blurry (but don't go cross eyed if you can help it). Your pupils are now dilated.
Now, open your eyes WIDE and suddenly focus as HARD as you can at your eye in the mirror. Make the picture as CLEAR as you can. You can feel your eye muscles tug a bit ... your facial expression will probably look angry.
You will see your pupils rapidly contract into unusually tiny points.
If you have blue or light green eyes like the person who showed me, this rapid change will look kind of creepy...if nearly black like mine then not so much, and I don't recommend running off and showing everyone, but you can still see it for yourself.