I remain confused about your definitions. From the Paul Graham article:
If willfulness and discipline are what get you to your destination, ambition is how you choose it.
This would suggest a definition of “ambition” as it is commonly used: the tendency to choose big goals. On the other hand, you say:
Some people seem “born ambitious” but there’s not a lot I can change my actions based on that.
Okay, now I have a little insight into your motivations for thinking about this: you want to become more “ambitious” yourself. But this suggest “ambitious” to mean rather something like “capable of achieving big goals”—you don’t need to attain the “tendency to choose big goals”, because that’s trivially easy, and anyway, if you care about this topic, that means you already have big goals.
So, does your question in the OP mean something along the lines of “how do people become capable of achieving big goals”?
Ah, yes, when I say “choose”, I mean system-2-choose (i.e. the former meaning in your comment). Learning how to
(i.e. how to work with setting intentions, or in general, how to overcome akrasia) would already be a to-do included on the big to-do list called “achieving goal X”.
In any case, if I understand it correctly, the question still is: how do people become capable of achieving big goals, including whatever system-1 manipulation, intention-setting, habit-forming, incentive-landscape-shaping, motivation-hacking, etc. is necessary to achieve these goals?