Real-world reference checks: Follow the investigative reporter rule "consider the source".
When I was first became a recruiter a little more than a decade ago, it struck me as odd that reference checking generally consisted of calling names given you by the candidate. Unless the candidate was an absolute idiot (and I'm sure we've all had a few of those . . .), those references generally put the most positive spin on a candidates skills and abilities. You've been handed the candidate's own rose-colored glasses through which you've been asked to regard his executive-ness in all his glory.
But there is a better way, one detailed by Guy Kawasaki in an article entitled “10 Ways to Use LinkedIn“.