Detecting Cross Site Scripting XSS Vulnerabilities With Fiddler

For those of you who have either subscribed to my Facebook profile or RHA's Facebook fan page, you might know that i have been on a mission to discover XSS on high profile websites, I have found XSS in high profile websites like Microsoft, ebay, apple, adobe, stumbleupon etc, Lots of people ask me the regarding the methodology i use in order to detect Cross site scripting vulnerabilities (XSS).