It all depends on who's doing the auction. You can sometimes drive by the property and see a notice posted in the front window or on the front door with a number to call, or a web address to go to online. With a little effort you can find this info. out.
I'm most familiar with the "sheriff sale" which will be posted somewhere in the county courthouse or county building & will be also be auctioned off with other foreclosed homes on the same designated day each month "on the courthouse steps" or somewhere similar. The foreclosing bank will have their own representative there to "open" the bidding @ a price they've determined is what they are owed. If you have the money, and want the house, you can place a bid for one dollar more than the banks opening bid and if there are no other people there wanting the same home you could become the new owner. But it is not "contingent" upon any lending, inspections, or apprasials. You just have to have the money available to you that day. Otherwise the bank owns it and then it will eventually find its way into a Realtor's care with a for sale sign in the yard.
Also, until someone has legal permission to enter the home, they usually cannot be "shown" until it has been assigned to a local Realtor.