How to work with foreclosure auctions?

[Elena Pech]

Hello, I found several homes on foreclosure auctions, and for most of them the sale was cancelled a day or few days before the auction. Two properties are still listed, but I found them on Zillow with Pending status. What is a right way to buy a foreclosure? Should I try to contact a bunk or a current owner? Can sale be cancelled because other buyers bought house outside of foreclosure auction?