Here’s a quick and simple tip for better portraits by Reddit user rmx_:
Everyone has a lazy eye. By that, I mean one eye is always smaller and/or more closed than the other eye. In some people, it is very easy to spot; in others, nearly impossible. The “beautiful people” have more symmetrical faces, but still, one eye will open more than the other. (Denzel Washington has one of the most I have seen [...])
[...] here is the tip: get the smaller/lazier eye slightly closer to the camera. Oh, and don’t tell the person what you’re looking at their eyes for! You’ll make them self conscious. Simply ask them to look at your finger and move their head to follow it, and then guide them left or right as necessary. Chances are, the movement needed will not be so much that you have to adjust your lights.
You can read more about how facial symmetry relates to beauty in this Wikipedia article.