Your best bet is to look at Notices of Default filed with the county. This will let you know who is behind on their mortgage. It is best for everyone if you buy a foreclosure before it is actually foreclosed.
A "short sale" happens when the buyer purchases the property for less than what is owed on it. The bank may agree to accept a lower offer to save on the expensive legal fees incurred when a foreclosure takes place.
There are additional benefits to you and to the seller. For you, you gain a wider selection of properties and beat the crowds to those that are most desirable. For the seller, they avoid the big red X a foreclosure puts on their credit--not to mention their psyche.
Pouring over Notices of Default isn't all that much fun, so why not make your realtor do that work for you? Your realtor can find the ones that match what your looking for, contact the seller, the lender, help you negotiate, etc and then sell it for you for a profit. I personally love this kind of stuff, so let me know if I can help you out with your bargain hunting!