When I tried on pairs of sunglasses I must've went through 20 pair till I got one that I liked the fit of. I think its something that you just get the sales clerk to open the display case, and then just start trying on glasses.
Try the Costas' if they have them. I have Smith Action Optics and love them, so try them also if you'd like.
First decide what lense color you want, grey, yellow, amber, etc. Then if poly lenses are fine, or if you want glass lenses. Poly is much lighter, but can scratch easier. I have glass lenses, but don't notice the weight at all, plus they're two years old and not one scratch.