It depends on what your model for purchase is. If you plan to get conventional financing, meaning a loan through a bank or other lender, then you really will be best served to find a realtor experienced with the area you want to purchase. That agent can help you shop the specific market and capture a good opporunity when it comes along. All short sales that I know of are sold through the MLS and with a licensed real estate agent, and many foreclosures are as well.
If you are a cash buyer/investor type, and you are hoping to buy at auction...that is an entirely different world. Frankly, it is not for the uninitiated, because there are no protections when you buy on the courthouse steps, and you have to be able to absorb all risk. You have to pay all cash the day of the auction, and you rarely have the opportunity to get inside the property before you purchase. There is NO title insurance. If you are still reading, you should be hearing alarm bells in your head at this point. When you buy it, you take responsibility for ALL liabilities. I tell most buyers this is really a fantasy scenario that it is best to not waste time on.
The people doing it are mostly professional and experienced investors, and most of them are pretty aggressive. Most use Foreclosure Radar as one of the resources for watching what is scheduled to come on the auction block. And, of that list, the vast majority gets pulled back at the last minute. Buying foreclosures requires a full time effort and an ability to leverage cash and absorb risk.
Hope this was useful, but feel free to contact me if you have further questions.