The most important things to get are UVA/UVB protection and polycarbonate lenses (or non-breakable). I assume you don't need prescription sunglasses, right? For those people who need prescription sunglasses (like me), I would recommend NOT going to your LBS for that but to an optometrist who knows sports glasses. Most to.

I love my Rx Tfosi sunglasses, but I got them through a bike shop and I really should have gone to the optometrist.