His process was to let them lie to him - he even encouraged it, all while he was recording the call. After the call ended he'd launch a legal claim for compensation and he'd always win.
For example if they implied he could be jailed for not paying him debt, he ask them to confirm what they must said and use that as evidence of a violation of the FDCPA.
His logic was that in the good days credit companies were begging him to take on debt, but when the economy crashed and he found himself out of work they weren't so understanding about his circumstances.