As much as it takes to get a buyer. As a listing agent I do my CMA, list the house at a midpoint of retail and indicate that it is a short sale. I will reduce the price on a regular, but not predictable basis until an offer arrives. Doing this I demonstrate to the lender my best attempt to obtain top dollar for their asset, but I don't waste time assuming a buyer will arrive at full price since it's a short sale.
As soon as I can put a sensible offer in front of the bank, I do. The reality is the first offer may get frustrated or distracted by another home and go away. If the process is started at a reasonable price we stand a good chance of a successful closing.
As a buyer’s agent, I'll make an offer at the low end of my CMA or whatever my client is willing to stick with while the process proceeds.
I know you said this is a question for buyers but I had to answer in case any buyers read this thread. Offers on a Short Sale should be based on a CMA done by the buyer's agent - not the list price. So, depending on the list price, the offer may need to be increased (for those agents who purposely listing way too low to generate offers) or decreased if the list price is over current market value.
SR Realty http://www.RealtyBySR.com