Prada items are so desirable that they have spawned a whole line of fakes. The fakes are sold by unauthorized dealers hoping to prey on those without the money to buy a real item. Prada shoes are one of the faked items. Any Prada shoes being sold at a very cheap price should be checked for authenticity.
Examine the shoe box. Real Prada boxes are made with corrugated plastic. If the box is cardboard, it is a fake. Prada spares no expense in the packaging, so you'll find them packaged and labeled professionally.
Look for the logo on the end of the box with the size and material information. Prada never puts the logo on the top of the box.
Look at the sole for the Prada logo in either an upside-down triangle or an ellipse. A fake pair of shoes may have the Prada logo on the side of the shoe, or not on the sole at all. Look for the Prada logo on any toggles or zippers on the shoes; a real pair will have the Prada logo on these items.
Check the date beneath the Prada logos. It should say 1913, the year Prada was established. A fake will often make the mistake of using 1931 as the date.
Examine the dust bag. The real dust bag is silver with a silver drawstring. A mesh or plastic dust bag, or a silver dust bag with a black drawstring are dead giveaways that you have found a fake pair of Prada shoes.
Try on the shoes. Prada shoes should fit snugly but comfortably. Fakes will not since they aren't made with the same quality standards.