You'll feel less like a pack mule when you're running errands if you try a compact messenger style that hangs diagonally across your body. Check that the stitching (particularly at the corners) is even and tight: It shouldn't budge or fray if you poke at it with your fingernail, says Mull. Opt for a lightweight leather (real or faux) or nylon that is durable but won't weigh you down when you're already carrying an armload of dry cleaning or a load of groceries.
The right size: A bag that rests on the curviest part of your hip or in front of your lower abdomen and is not too much larger than a DVD.
The most common mistake: Chain straps easily slide off, dig into shoulders and add unnecessary weight. Look for a flat, broad strap that is more forgiving.
One to try: A bold pattern with personality is good for off-duty hours—like the watercolor-inspired florals and graphic tribal prints seen on everything from accessories to dresses at shows like Jason Wu and Michael Kors.