Last week one of my Writing with Flannery O'Connor students asked,

Do you have any tips for describing people's physical appearances and expressions? I've been trying show, not tell, their personalities and emotions, but I'd like to avoid cliches such as 'she had a heart-shaped face' or "his eyes shone." 

That's an excellent question; it can be very hard to convey a character's physical appearance. So I thought I'd share my answer with the rest of you.

When you are describing anything in writing--a person's face, a room, a landscape, anything, really--it is important to ask yourself how much description you need. Your goal is to give your reader just enough to look at so that he feels that he can envision the scene. But it's a bit of a magic trick, and a bit of a balancing act, because you are actually just giving the reader the impressionthat he can envision the scene. If you provide too much detail, you actually pull the reader out of the scene. 

When it comes to describing a person's physical features, one or two interesting or unusual features are worth a whole lot more than five or six forgettable physical features.