Dr. Michael VanPelt of the University of Texas Southwestern Medical Center says most people's feet aren't exactly the same size, so one new shoe may feel different from its mate, but neither should feel too tight.

"Measure both feet and ensure shoes fit the larger of the two," VanPelt says in a statement. "A good rule of thumb while shopping (for children's shoes) is to allow at least one finger's width from the end of the longest toe to allow room for growth."

Ill-fitting shoes can not only pose problems in proper foot development but can also lead to leg or back pain due to poor posture.

"It's best to shop for shoes in the afternoon or evening, because feet naturally swell during the course of a day," VanPelt says. "For children, avoid backless shoes, as well as footwear with high heels, which pose greater potential for injury and can hamper proper foot development. Look for soles that will provide good traction and shoes with good arch support."