I think the best idea is to go to a store (sunglass hut or wherever), try a bunch on, and figure out what the best one for your face is. Having an unbiased female opinion is a HUGE help.
I have a pair of Oakley's (third one of these) and I think they're pretty generic. Then, I went into the store, elicited a female's help and wound up with a great pair of
Pradas a year ago. Have gotten a bunch of compliments since then.