Photo: Courtesy of the Limited
The right size: Something roughly the size of a cereal box that doesn't jut out more than six inches from your body.
The most common mistake: Choosing straps that are too short or too long. Make sure that your bag can be easily swung over your shoulder (with the top hitting at the middle of your ribs) but doesn't drag on the ground if you carry it with one hand.
One to try: A two-tone tote made of contrasting colors doesn't just add style to a standard shopper—many brands (like C. Wonder) feature versions with a darker color on the bottom so that you can set it down at the grocery store or under your desk without worrying about stains.