If the eyes are the window to the soul, being able to manipulate how your eyes appear to others is a rather tricky lifehack. Over at WikiHow they have a tutorial on methods of training yourself to shrink and enlarge your pupils. Why might you want to do this?
Scientists have actually studied how the way we feel about the things we see affects the size of our pupils (welcome to the world of pupilometrics). You can gain some insight as to how someone feels about you (or someone or something else) by observing changes in their pupils, and you can also affect the way someone feels about you by changing the size of your pupils!
The tutorial goes on to elaborate on several methods all of I, as your dutiful editor and purveyor of fascinating lifehacks, put to the test. In my unscientific testing, the most effective trick on the list was number two:
Look in the mirror. Try tensing your stomach in a variety of ways and see if it increases your pupil size. Some people can dilate their pupils in this way, although the underlying mechanism is unidentified. It could be connected to the feeling of "butterflies in your stomach" that you get when you like someone.
Or perhaps connected to the deep belly laughter of a maniacal genius bent on world domination! If you test out any of the odd (but safe) methods listed in the article, share in the comments below.