The best advice would be not to try it without some kind of professional assistance. If you choose not to use a Realtor who is experienced in short sale negotiation, then you should at the very least consult an attorney who specializes in real estate. You will also want to consult with a Tax advisor regarding any possible tax ramifications This is not something you want to try yourself.
A good resource for folks in a difficult housing situation or nearing forecloure is
Your first step in commencing a short sale is to contact your lender for a short sale/payoff packet. After receiving the lender's short payoff packet you may want to contact a Realtor that does short payoffs. I have on my staff a short payoff coordinator that works very closely with your bank. I personally work with short payoff clients and ensure this process goes as smoothly as possible. We have been very successful in negotiating with the lender to approve and accept the short payoff. This is a very complex process that usually take an extensive amount of time to process. I would like to speak with your further regarding this process. You can not received a penny from a short payoff, but lenders will pay Realtors to broker this transaction. So, to get a Realtor to do this transaction for you literally does not cost you anything if the lender forgive your debtness in full. I can be reached at 719-265-9203. Thanks. Mike.
To get started I would go to http://www.ColoradoForeclosureHotline.org or call them at 1-877-601-HOPE. This site and their hotline are excellent resources for you. Most of the time short sales are a very long & drawn out process even when you have someone working with you that has done them before. Also know, the bank you are hoping to negotiate the short sale with will pay the real estate commissions, because of this I would encourage you to find an agent that specializes in these. Personally, I do not assist with short sales, but I would be more than happy to refer you to someone I know that does.