They lead by example and exude the personal and professional character that others are willing to follow to achieve the highest goals.
They have a historical successful track record that is easily verifiable and quantifiable. They know what they did and how. They can speak specifically to their impact and results. Their background is filled with examples of multi instances and situations where they reached specific high goals that they set, or they accepted the responsibility for the required thoughtful planning, utilization of all available resources, massive effort, overcoming of obstacles, rebounding from mistakes (and making few of them) required for achieving greatness.
These repeated successful results across varying scenarios provide clear evidence of a pattern of over achievement and transferable skills and competencies that are always found in Rainmakers.