The answers below are all good. But keep in mind, the bank wants to recoup as much money back as possible. The lending bank is taking a big hit. They might do an appraisal before approving the short sale to assure the offer is close and if not wait for another to come in higher and or all cash. If it is a low ball offer, the approval could drag for weeks.
Your listing agent should be in close communications with the bank. Follow-up with your agent on a regular basis. They are usually working really hard on your behalf with a short sale.
Confirm all the documents and information needed to make the deal go through are landing not only on the desks but in the hands of the right people. Get proof, like return receipts via the us mail or cc'd emails etc...
Daily or every other day phone calls go a long way too in making things move forward.
Congratulations on getting the offer. Your listing agent is your partner and together you will get this done.
Best to you in your sale.
Dan
If you like my answer please let others know. Thx. - Fri May 18, 2012