Feel it in your feet
Jason Schwartzman was asked by Terri Gross if Bill Murray ever gave him any advice about acting.
He claimed it was odd advice, but that it was good advice, and that he took it. It, roughly, follows:
Jason asked Bill if he could tell when he was in character. Bill asked Jason how much he weighed. Jason said he weighed 140 pounds. Bill asked if Jason could feel it (the weight) in his feet.
That is all.