I would choose a running-specific store, like Road Runner (is that the big road runner sports that has a huge website and catalog business?) or Fleet Feet. Even better, look for a local non-franchise running store. I wouldn't go to the New Balance Store, if its just a regular store in the mall. You never know how much training those associates get.
Whatever store caters to the hard-core running community in your area should be great for shoe fitting, even if you are just looking for beginning fitness shoes.
Tarah
Mama to the Forrest Creature 3/04 and Baby Ber 4/07
"All true wealth is biological" Cordelia Naismith Vorkosigan