If you consider your face a canvas, glasses add an element of line and shape. The first step to finding suitable glasses is to take a good look at your face and try and note not only the overall shape but the kinds of lines within your face. Are they long and straight? Rounded? Angular? The basic rule is this: like accentuates like, while opposites create a contrast. If you begin with a good assessment of your own face, it can help you decide which strategy to use. If you have a round face, do you want to accentuate that aspect, or do you want to achieve a more balanced overall look?