Psychologists Susan Murphy and Stefanie Johnson in their recently-published review of the "early seeds of leadership," suggest leadership tasks and skills that can be developed as early as 2 years of age.
Here is what they suggest parents should work on developing at particular ages.
Preschool years (ages 2-5)
Delay of Gratification. This is the early root of emotional intelligence - learning to control desires and learning to wait for rewards.
Communication Skills. At this early age, work on the basics of emotional and nonverbal communication (e.g., reading emotional faces), and on social skills, including using words to influence others and to communicate liking and affection for others.
Elementary school (ages 6-11)
Working in Teams. Coordinating efforts and cooperating with others.
Public Speaking. Ability to express ideas to others (which also develops basic social skills)
Early Leadership Tasks. Volunteering as class monitor or teacher's helper; leading student projects.
Middle school - early adolescence (ages 12-14)
Self-Mangement Skills. Learning to better understand oneself and to critically evaluate oneself; goal-setting.
Leadership Tasks. Coordinating student teams and public speaking in a leadership role.
High school - late adolescence (ages 15-19)
Organizational Skills. Coordinating and leading complex projects. After school and summer jobs help.
Motivational Skills. Learning how to motivate others; delegating and monitoring the work of other team members.
College - young adulthood (ages 19-22)
Establishing Organizations. Starting or leading a school club; founding a grassroots organization
Supervisory Skills. These can often be learned during summer internships or part-time jobs.
Leadership Skills. Focusing on leading multiple constituents and diverse team members.
This comes from an article in a recent special issue of The Leadership Quarterly. In those studies, the early roots of adult leadership are traced back to adolescent and childhood years. The results are fascinating and represent some of the first longitudinal studies of leader development.