As long as you make sure to take the extra precaution, then the process of making offers on those properties is basically the same as making offers on any other properties.
Also, it's not enough to work with an agent who specializes in (pre-)foreclosures, short-sales, and REOs. You also need to make sure s/he has experience with making offers on properties in bankruptcy. Afterall, you wouldn't want to learn 6 months or so after the fact that the bankruptcy judge disapproved of and cancelled your purchase, and has signed an order to evict you immediately. (Although that's kind of extreme and it doesn't always happen, it's certainly possible and has happened from time to time.)
As for your question about what a Buyer can do and when etc -
Here is what you can do:
Contact a Realtor with Certified Distressed Property Expertise to help you through the Short Sale buying process.
They CDPE Realtor can assist the homeowner/seller through the short sale process, help them avoid the dangers of foreclosure and save them alot of confusion during the process.
Please understnad that a homeowner in financial distress and hardship doesn't know where to turn, or at least that's my experience with assisting homeowners and buyers of distressed property. They are confused, hurt, not thinking clearly and can also be angry at the situation they may be facing - FORECLOSURE.
Buyers are wanting to get 'a good deal' but most do not know how to go about a short sale or buying an REO property form the bank and can easily get dis-heartend with the whole confusing process.
Let an expert help you AND the distressed seller... that's my advice... :)