Find frames that are shaped differently than your face. So for example, if you have a round face, try and find a pair of angular shaped glasses. If you have more defined, angular features, you may want to go with a curvier or rounder frame.
Try and keep everything in proportion. So if you do happen to have a smaller face, than go for a smaller lens. Our main goal is to blend in and not draw too much attention, so a frame that is way too large or small on your face will most definitely draw some attention.