First: Advertised foreclosures may happen on the date advertised or the homeowners may get extensions. So if you get some interest in a property, be prepared for the dates to move, or the auction could get cancelled altogether, if the owners find themselves out of trouble.
At the Auction: Foreclosures/Distressed properties tend to have more risk associated with them than conventional properties. You go to an auction with a non refundable down payment, if you are the winning bidder. You then have a fixed period(Frequently 30 Days) for which you have to come up with the balance. (or risk losing your deposit)
Because it is more difficult to get conventional financing on foreclosures, many buyers are cash buyers. Then as a cash buyer, you are not going in with a bank, so you need to make sure that you are not taking on any title risk or are subject to unexpected liens. Most of this research should happen before the auction and before you win the bid, so that you know what your risk and burdened cost will be.
There in lies the rub. In a conventional sale, you pay for legal legwork as part of the closing process.(predictable) In a foreclosure, you will have to do all this research yourself(or pay someone to) on all the targets you are interested in, that may or may not make it to the auction block.(unpredictable)
The alternative is, as another agent stated, wait for the bank to take it, and buy it from the bank.