If the BIN is ridiculously low (like $350 for a really popular pair of shoes) that should be a red flag since the auction is designed to prey on impulse buyers who just skim over the auction without reading details. Occasionally sellers do sell authentic pairs for a low price but this is like finding a needle in a haystack.
Also, if there is no mention of "authenticity" (sometimes sellers will leave this out on purpose). Always do a feedback check and if you're really uncertain post the auction on the authenticity thread. If you actually receive a pair of fake shoes you will be able to tell by the craftsmanship right away that there is something odd. Compare it with an authentic pair of CLs and you will probably notice the difference right away!
Also, if there is no mention of "authenticity" (sometimes sellers will leave this out on purpose). Always do a feedback check and if you're really uncertain post the auction on the authenticity thread. If you actually receive a pair of fake shoes you will be able to tell by the craftsmanship right away that there is something odd. Compare it with an authentic pair of CLs and you will probably notice the difference right away!