Yet mentors are not all created equal. Like housekeepers or mechanics, good ones are tough to find.
Mentors take an active, guiding role in the career of a less experienced person.
They should not be thought of as therapists, career coaches or good contacts. Of course, any strong mentor takes on all of those roles at times. Mentors aren't necessarily executive stars. Often a relationship with a supervisor who takes a genuine interest in your future will evolve naturally into mentoring. Don't count on it, though.