iPhone 4S I did upgrade and hate it, want to go back
I am sorry to tell you that there is no official way to downgrade from iOS7 to iOS6 anymore as Apple stopped signing the 6.1.4/6.1.3 firmware. Every time a software-upgrade is done iTunes asks for a verification of the firmware. As of 21st of September Apple stopped signed the 6.1.3/6.1.4 firmware and therefore iTunes will refuse a downgrade to iO6. For more information see the following blog for more information.

update: this question has already been answered over here: Can I undo the upgrade to iOS 7 by restoring to iOS 6.1.3?