Go down a size if the shoe has lots of excess in the toe or if your toes slide forward when you move. Go up a size if the shoe feels uncomfortably tight or the back digs into your heel. The shoe fits properly when you don't have to tighten the drawstring, your heel stays in place, the tips of your toes fit almost to the tip of the shoe, and you have room to wiggle your toes. As a general rule, a wide foot requires a wide shoe. Split sole shoes fit the same as full-sole shoes.
Soft shoes tend to feel stiff and move on their own when new.
Soften with a bit of shoe oil to make them more comfortable. Use rosin on the entire sole of the shoe. Though a proper-fitting ballet shoe should have almost no room in the toe, do not confine a child's foot in too snug a shoe. Change shoes when growth occurs to prevent injuring the foot. Inc. How things get done.