PS: I couldn't fit the question mark.
1. Identifying and trying to solve problems, then seeing how well you succeeded. Come up with something you want to exist and make it. It could be as simple as designing and 3D printing an object, then taking it to a craft fair to see whether people like it.
2. Basic business operations. What's it like to explain a product to a prospective customer? How about collecting money or delivering the thing you sold? What's it feel like to have to price your thing? Ideally, start a company while you’re in high school, even if it’s selling professional services and you only get a few customers. All the better if you have time to create a product or app or something.
With 1 and 2, by the time you start a full-time company, you've already experienced most of the "rookie" emotions that any first-time business operator has.
3. Going against the typical path (based on your own analysis of a situation, not merely to be different!), being an underdog, and/or intentionally accepting uncertainty. A simple example might be joining a LGBT+ club at a school where LGBT+ students and supporters aren't appreciated. Join debate club or Toastmasters and advocate for unpopular positions. Get used to people thinking you're doing the wrong thing (like, oh, starting a company instead of taking a job, or creating a product that everyone thinks is a toy) and hearing their reasoning. Get good at explaining your reasoning for and belief in something.
1 and 2 can pretty easily happen together. 3 is probably different.
One education tip: if you go to college, try to either graduate without debt (like by working a part-time job while attending in in-state public school), or attend a top 10 school. Don't take $75k worth of loans to go to some random private college; you'll end up with the same degree someone else has and a lot less freedom to take risks.