Good question this. Realistically, I think this may take a few blog posts to give a comprehensive answer to this very broad question. So Part 1 it is, not sure how many parts it will take...
I'm going to assume here that you are at school or college. I do not know may toddlers who have expressed an interest in graphic design, my three year old son will occasionally crayon on the wall, but I see this as tagging rather than any other form of typographic inclination. So let's assume you are at school and thinking a job in graphic design might be for you.