NFL.com has posted a great article on Parcells which is actually an excerpt form Charlie Weis' newly released book titled "No Excuses". I highly recommend that everyone read the whole article as Weis gives some insights on how Parcells is a master pyschologist who manipulates everyone around him, including the media. Here is a blurb on Parcell's technique of "button pushing".
My button was him questioning how hard I worked. I always worked hard, but he would say things like, "So, I see you're trying to get out of here early again, huh?"
It never failed. I felt I had to work even harder every time he said that.
Bill did it with everybody. It didn't make any difference whether it was Bill Belichick, our defensive coordinator at the time, or Ron Erhardt, our offensive coordinator at the time, or the equipment guys. Everybody was fair game. Bill would find the right button to push. He would play all kinds of mind games.