If you are new to ballroom dance, it can be helpful to know how to go about buying your shoes. Here are a few resources that you can check out for tips on getting a good fit:
Showtime Dance Shoes – tips on both fit and caring for the shoes.
About.com – tips for choosing the right style, construction and more.
MIT Ballroom Dance Team – top notch tips on just about everything to do with ballroom dance shoes.
No matter what the dance style, having shoes that fit properly is key to having a good class or performance. Hope these resources help!