1. Look for shoes designed for your foot type (flat/normal/high arch) and how you pronate (under/normal/over). If you're not sure, consult a podiatrist or store manager for help, or visit Runner's World's online shoe guide.
2. Sizes may vary among brands and styles. Try on a variety of shoes so you can make a good comparison.
3. Go shopping in the afternoon or after a workout, when your feet are larger. Feet can swell as much as a full shoe size during exercise.
4. Try on shoes with the socks, inserts, or orthotic devices you plan on wearing.
5. Try on both shoes―they may not be made symmetrically, or one of your feet could be slightly longer or wider than the other one.
6. Make sure the lacing area and tongue are padded to protect the tops of your feet.
7. The toe box should allow your toes room to move comfortably. When laced, the middle of the shoe should hold your foot snugly so it doesn't slide forward and jam your toes with each step.
8. The heel counter (inflexible material surrounding the heel) should fit snugly so your heel doesn't slip and move around.
9. Don't just lace up and look in the mirror: To get a good feel for the shoes, walk and jog around the store a little bit. Climb stairs, too, if possible.
10. Don't purchase shoes that feel tight, expecting them to stretch to fit.
Sources: American Orthopedic Foot and Ankle Society, American Running Association