There are 2 things people consider when selecting a pair of sunglasses -
fashion and function.

Function:
Many people use sunglasses for a specific activity, like boating, driving, skiing, biking, or lying on the beach. Each activity demands a different function such as reducing glare when boating or providing protection from wind and foreign objects when biking. Sunglass technology has advanced significantly in recent years and the number of choices available can be overwhelming.

To polarize or not to polarize: If you spend time viewing reflective surfaces such as water, car windshields, or snow, or if you find that your eyes are especially sensitive to sunlight, you need polarized glasses. All sunglasses block reflective light, but only polarized sunglasses block reflective light and reflective glare , the light that makes you squint and gives you headaches. A good pair of polarized glasses will eliminate these problems and will improve your vision under conditions where glare occurs.

Do darker lenses provide better protection? No, polarized glasses provide better protection. In fact, a light-colored polarized lens will provide more protection than a dark-colored non-polarized one.

How can I prevent sunlight from coming from the side of my glasses? The only way to prevent sunlight from coming in the sides of your glasses is to wear a wrap, but wraps can be uncomfortable and fog up. Many people believe the bigger the lens, the better the protection, but bigger lenses allow additional light to enter from the side. Anti-reflective coatings added to the inside portion the lens do not prevent sunlight from entering from the sides of your glasses, but it will prevent light from bouncing back to your eyes.

What color lens is best for you? What color do you like best? All colors provide sufficient protection, although in extreme light conditions, gray is best. Basically, it's just a matter of function that determines which color is best for you. Amber, Brown, and Rose lenses are best suited for sunlight conditions encountered in this area ( Mid Atlantic).

Should I be concerned about UV protection? No, all sunglasses sold in the U.S. purchased through reputable channels are regulated by the FDA and offer UVA & UVB protection.

Should I wear glass or plastic lenses? It all depends on the function. Glass lenses are clearer and less prone to scratching than plastic lenses. Plastic lenses are lighter and less prone to shattering than glass lenses.

Should I wear plastic frames or metal frames? Again, it depends on the function. Plastic frames are lighter and more durable, making them more resistant to impacts encountered during sports activities. High tech metal frames such as titanium are also very desirable.

Fashion:
Although many people select glasses based on the style, they will find they can also serve specific functions such as polarized lenses to reduce glare. Like finding an outfit that looks good on you, appearance is more important for fashion glasses than function. Many of the major clothing designers carry a line of glasses.

What lens shape or frame style looks best on me? There is no simple answer to this question. Often it is simply a matter of putting the glasses on and looking in the mirror. When you find the ones that look the best you will know. It is important you find a pair of sunglasses that you like so you will wear them. They will not give you any protection at all if they remain in the case.