Here are a few things to consider for those who’re looking to find the perfect pair (from Cosmopolitan and All About Vision):
The shape
The shape of the frame must contrast with your face shape (e.g if your face is round, angular glasses might suit you better).
The frame size
Sometimes, the frame size might either be too small or too little, so be sure to pick one that won't overwhelm or underwhelm your face.
The colour
Pick a colour that matches your features. This is a very subjective (and a tricky!) decision. Only you can decide what looks really good. Sometimes the colour may look good with your face, but you might not personally like it yourself.
Your best feature
Your eyewear should bring out your personal best feature (e.g If you have green eyes, consider buying green glasses).
Having a visual guide
Check out this nifty illustration of face shapes and the right glasses for them:
Image: www.scoutsixteen.com