We originally had my son fitted for ballet shoes at our local dance shop (which I do recommend for first time ballet shoe purchasers).  At the time, he wore a size 1 street shoe and had a slim, narrow foot.  The salesperson fitted him into these Capezio Teknik ballet shoes in a size 2 C (both one size up from his street shoe AND one width up).  The fit was perfect.  They have held up very well through his once weekly ballet classes, although the little ties frequently come undone.  Although the shoe is still in great shape, he has recently moved into a size 1.5 street shoe so I saved myself a trip to the dance shop and ordered the size 2.5 C from Amazon (since I now understand how the sizing works).  Great shoe overall.