There's no single answer because it's a function of how you learn, and the subject matter in question. I'm one of those people who doesn't believe that anyone can learn anything -- there are some constraints (despite having a growth mindset) that will limit how far you can go.
I think semantic tree/first principles/physics-based approach (popularly attributed to Elon Musk) is one way to approach it. It's actually a really difficult approach and you need a certain level of intelligence and personality to do it well, so it's not for everyone. I can do it to some extent but it's actually really difficult to hold lots of ideas in tension and to be questioning all the time -- it's just not my thinking style.
The other approach is what many smart (but non-geniuses) take: the buffet approach. You graze at the table of books, Wikipedia, online articles, and hang out in online communities (like Twitter) to overhear what experts are discussing. The thing about most areas of knowledge is, there's usually only 20% of the subject that matters--the rest rarely come up (Pareto Principle). To know what 20% to focus on, you need to understand the sociology of the subject matter and what experts think are important. Unlike the previous approach, you won't have watershed-level insights, but you'll know enough to be considered "educated" on the subject.
I think semantic tree/first principles/physics-based approach (popularly attributed to Elon Musk) is one way to approach it. It's actually a really difficult approach and you need a certain level of intelligence and personality to do it well, so it's not for everyone. I can do it to some extent but it's actually really difficult to hold lots of ideas in tension and to be questioning all the time -- it's just not my thinking style.
The other approach is what many smart (but non-geniuses) take: the buffet approach. You graze at the table of books, Wikipedia, online articles, and hang out in online communities (like Twitter) to overhear what experts are discussing. The thing about most areas of knowledge is, there's usually only 20% of the subject that matters--the rest rarely come up (Pareto Principle). To know what 20% to focus on, you need to understand the sociology of the subject matter and what experts think are important. Unlike the previous approach, you won't have watershed-level insights, but you'll know enough to be considered "educated" on the subject.