I go to all sorts of pet stores, but when I really want good advice about something to do with my dog, fish or crab, I go to Pisces.
First of all, it's huge. Second of all I've never gotten bad advice from the staff there. They really know what they're talking about, and if they don't know they'll ask another staff member.
They have specialty pets, products and a humongous saltwater sealife area...and lots of parking!
I find that the brand of dog food that I buy is usually cheaper at one of the chain pet stores, though.