It used to be that sporting glasses was reserved for nerds like Lewis and Gilbert above. There was a stigma attached to it, so the people who did wear them only did so because they absolutely had to, and/or because they didn't really care that much about their appearance.But over the course of the past decade, all that has changed. There are tons of options for stylish frames, and glasses are now used as a tool for expressing one's personal style. Check out heartthrob Jon Hamm in a classic black frame below. The look is clean, confident and smart.If you're thinking about updating your look, glasses are a fantastically handy way to do so. Read on for my tips on choosing a pair of frames. And by the way, if you don't need glasses, don't feel left out. Plenty of people sport specs sans prescriptions.SHAPE1) Angular-shaped glasses read as authoritative, while glasses with rounded shapes make you look approachable.2) There's a lot of information out there about what shape faces should wear what shape glasses. To me, it's less about rules and more about choice. If you wear the same shape glasses as that of your face, you'll reinforce that face shape; if you wear the opposite shape, it will balance your face shape. So there's no "bad" or "good" here. Rather, it's what you choose to play up. As a specific example, if you have a round face and want to look tougher and more commanding, I recommend wearing glasses that are squared off. Luxottica CEO Andrea (above) is doing just that.3) The sides of your glasses should end between the corners of your eyes and the sides of your face. (However, if you have a long and narrow face and want to balance that, look for shapes that extend slightly beyond your temples so as to create width in your face. Also, people with long and narrow faces should avoid very small frames.) COLOR AND MATERIAL4) A very dark frame can make a strong, dramatic statement (it's also trendy). If this is what you're going for, be careful that the dark frame doesn't overwhelm your own coloring. Check out the guy on the left above -- his own coloring and features stand up to the heavy frames. In comparison, the dark frames on the right dominate Brad Pitt's facial features. On him, you see the frames first before you see his face.5) Choose a color or type of metal that works with your own coloring. If your skin tone is warm, go with warm-colored frames; if it's cool, go with cool-colored frames. Hint: if you have grey hair, a silver frame can play off of that nicely.6) Metal frames have a more modern and dressy feel, and plastic reads more casual. Tortoise frames have a preppy and collegiate vibe.7) Avoid transition lenses, as they often end up in an unflattering middle-ground of lens color -- not quite dark enough to be sunglasses and distractingly shaded for when out of UV-light. They also don't darken inside vehicles, so they don't work as driving glasses.DETAIL8) If you have a broad nose or wide-set eyes, go with frames that have a darker nose piece or bridge, as this will make your nose look smaller and bring your eyes closer together visually. A light nose piece will "open up" the space between close-set eyes and make them appear farther apart.9) Think about whether you want a logo on the side or not. I often find that the more heavy-handed logos can cheapen a look. One brand that I love for its subtlety is Persol (see above) -- its logo doesn't say the brand name anywhere. It's just a classy-looking design.PROPORTION10) The lenses should leave just the right amount of space around your eyes: not so much that they're out of proportion to your features, but not so little that they crowd (and therefore diminish) your eyes.FIT AND FEEL11) When you try on frames, think about how they feel physically. Are they comfortable? This is important, as they'll be hanging out on your face all day.12) Be careful not to get frames that are so heavy that you're constantly pushing them back up your nose.When you're shopping for glasses, find a store where they take pictures of you in the different contenders that you can look at on a screen side by side. You can also bring a camera and compare photos yourself. Glasses are an opportunity for you to show some personality. So take your time and have fun choosing a pair that works for you and that helps create your own individual look. And of course once you find a pair you love, you can start expanding your collection so that you have different glasses for different occasions.Do you have a favorite pair of glasses? If so, what do you love about them?