Your hair color (natural or otherwise) can have a big impact on which frame colors will work best for you. Consider not just the shade of your hair (brown, blonde) but also whether it has cool or warm undertones. This quick list will get you pointed in the right direction.
Playing off your eye color can have a subtle influence on the overall look of your glasses.
Selecting frames close to your eye color will reinforce your natural palette and create depth. Choose contrasting colors for a more dramatic effect that will make eye color pop.