At that point, I started reading books (I was about 15), my first was rich dad poor dad (which had no real substance besides widening my prospective). Then I started reading real estate books, then 'business' books, automotive books, medical books, biographies, books on philosophy & finally programming books (where ie settled for now). Along with that I started making friends with the 'smart' & 'creative' kids at school, which led to meeting 'rich' & 'successful' people and being able to observe, what I thought, were their strong and weak points.
I feel that 'self-starting' comes from awareness that you can do whatever you want and become successful. How you reach this awareness, I'm not sure (my path was basically family, books, new people).
disclosure: i am on my mobile, so my grammar and spelling may be more off than usual.