My view is don't do it. What looks smashing and hip in extreme youth tends to look much less so as you age.
There is also something about things like piercings and other body alterations. There is a "moment" (a few years) when they effectively signal a certain "otherness" and make a statement. After that, they signal, "I am signalling my otherness by doing what everyone else does," and the impact is lost. Right now, that shift is occurring with earlobe-stretchers, and it will soon occur with the body-scarring that some kids have turned to instead of tattoos because tattoos have become too mainstream. (Guess what, kids, your scar patterns will too, or they will never go mainstream at all, and you will have permanent results of a minor fad. Either way, the permanence is a problem.) A permanent alteration to the body that will turn out to have been a trend is, in my view, never a great idea.
Unless the alteration is part of a cultural tradition that is your own, it *will* turn out to have been a trend. A trend that lasts a generation is still a trend.
The fun of fashion is that it doesn't last, right?