First make sure what kind of facial structure you have by looking at your face through the mirror.If you have a round face, then the rectangle or square frames might suit you fine. If you have an oval face, then any kind of sunglasses will look good on your face. Go to choose these sunglasses online, they are much inexpensive than the real store and they also make you look decent.
What face shape do you have. People who have different face shapes suit different kinds of sunglasses. I think the most effective and quick way is to try on sunglasses. Whether you buy sunglasses in online stores or retail stores, you can try on any sunglasses you like. Even while choosing sunglasses in online eyeglass stores, you can try them because almost every online sunglasses store offer Try-on System and you will see how you look with their sunglasses. Trust me, choosing sunglasses is not that hard. Good Luck.