A full answer to this question would vary from individual to individual but anyone asking it would benefit from looking at their work-related future for a moment and asking, "Where is my career going and how well has it progressed so far in that direction?"
If the answers don't come easy, think back to the last time you made a career decision. What influenced your choices at the time? Who else played a role in the decision making process? Were promises made regarding your future? How would you measure your progress since that decision was made?
If your answers prove that you know where your career is going, that you are happy with your career direction and your progress along it, there is a good chance you are already leading your career.
However, that does not make less conclusive answers a bad sign. By gathering this evidence you have taken important steps towards understanding and leading your career and towards creating new opportunities for personal success.
Enjoy the weekend ahead!