"Measure leaders by the number of people who worked for them who have gone on to bigger and better things."
After I became CIO of Medtronic, during my first staff meeting I was asked, "How are you going to measure your success?" My response was, "By creating 5 more CIOs." Someone then said, "But there is only one CIO position at the company." I replied by saying, "That means that four people will get CIO positions outside of the company." Well, five people within my IT organization did become CIOs. Several were not direct reports when I first became CIO.
In order to develop people, you have to give them exposure to others who can give them better opportunities than you can. Weak leaders horde their talent and feel betrayed when they leave for better opportunities. The way I knew I had done a good job developing them is when someone else wanted them. That's the way leaders build a strong leadership pipeline--people want to come work with you because they know they will get better opportunities within or outside of your organization.
I developed this mindset by watching how the CEOs at Medtronic and Georgia-Pacific developed people who went on to become CEOs at other companies within the industry. (As a side note, there are also now 4 people who worked within my IT organization at Georgia-Pacific who are now CIOs.)