4) Focus on the teacher, not the topic
In my experience, you learn more from great teachers than from great syllabuses. I had too many classes taught by droning bores. I didn't show up, even when I was sitting in the chair. I didn't learn much.
When I think about the classes that shaped me the most, I think about my Marxist Canadian history class, taught by a socialist ideologue. There is not a lot of demand for Canadian history outside of Canada, whatever version you learn, so I can't imagine a situation where I'd apply any of the facts I learned. But the professor was a master at engaging us students in vigorous, often passionate debate. I learned to think, and to challenge some of the basic assumptions I had about my own society.
I tell my own students to pick eight or nine classes based on the syllabus, to go to them all, and then keep the four or five classes with the most engaging professors.
5) When in doubt, choose the path that keeps the most doors open
If you're like most students, including me at that age, you have no idea what you want to be when you grow up. In cases like this, try not to narrow your options. Sure, take the boutique courses. But stick to mainstream majors, ones with plenty of options at the end: the sciences, history, economics, politics, and so forth.
Take the classes that are the basis of social and natural science: statistics and math.
Plenty of courses in the humanities are also building blocks. With the right professor and syllabus, a history or political theory class will teach you to argue, think, and write. These take more searching, but they are there at every university.
Other basic building blocks might be computer science and, as I mentioned above, writing.
6) Do the minimum foreign language classes
This is one of my most controversial pieces of advice. A lot of people disagree.
Languages are hugely important. And you should learn another (or many others) besides English. But I think they're better learned in immersion, during your summers or before and after college. Maybe take an introductory course or two at university to get you started, or an advanced course or two to solidify what you already know, but only that.
Statistics are not more important than languages. But the opportunity cost of skipping a statistics course is high because it's hard to find ways to learn statistics outside the university. Remember you only get 30 or 40 courses at university. There are a dozen other times and places you can learn a language. Arguably they're better places to learn it too.
I feel the same way about most business and management skills. They are critical to a lot of professions (even academia), but classrooms are poor places to learn them given the alternatives. Exceptions might be more technical skills like finance and accounting.
Note that I say all this as someone who doesn't really speak another language well. I can travel in French and Spanish (barely), and I regret not being any better. But I don't think taking more classes in college would have helped this. I should have made other life choices, like living abroad. This brings me to my next point...