Let’s face facts: Most boards invest heavily in executive assessments, exposing chief-executive candidates to C-suite responsibilities and checking their P&L performance — while simultaneously scanning outside prospects.  Yet less attention is given to one of the most important determining factors of all:  Whether directors who have actually served as CEOs are driving the process.  It takes one, in our view, to really know one.  If the succession and search are not driven by those who have already run another firm, the company is, in our experience, less likely to end up with a CEO who can run this one.