If you have been treating this property as a rental, you will have to complete Form 4797, Sales of Business Property.
There is not much simplicity when you're selling a rental property. You will have to take many things into consideration-- list your purchase price of the home, things you have done to increase the basis of the home, list your sell price of the home, and, importantly, if you have been taking depreciation on the home, that will be added to your added to your basis in the home. Depending on how big of a loss you're looking at, how much depreciation was taken, and additions and subtractions to the basis, you may not actually be looking at a loss.
My advice is to go through Pub. 523, Selling Your Home. http://www.irs.gov/app/vita/globalmedia/p523.pdf
Look at the things that are added to the basis. Also, look at the selling expenses you may use. This will help you sort out whether or not you will have a loss or a gain. Either way, you will use Form 4797 to report the transaction.
Please let me know if I can assist you further. Also, please consider seeking a tax professional or accountant in your area to assist you with filing your taxes when you complete this sale, as the smaller details can make big differences and mistakes can cost you.