Something that helped me establish a solid ground as a freshman:
1. This is possibly the only year where almost all your attention can go to getting good grades. This is also when classes are the easiest. Yes, people are gonna complain that genchem is hard, etc etc but a lot of work =/= conceptually hard course content. Freshman year generally is the easiest year to get good grades, so shoot for a 4.0 (I did and got it, and it really has helped me mentally sophomore year)
2. RATEMYPROFESSORS. If you wanna get a 4.0, working hard is one thing, but playing smart is another. Find a professor that is known to not grade harshly and throw out random exam questions. Ratemyprofessors has that (may be biased, but most of the time the reviews on there are correct).
3. Courseload. Kinda going off of #2, gotta play it smart. Although admissions from highschool -> college may have preferred a slightly lower gpa for taking extremely challenging courseloads, not for this type of admissions. High gpa > hard courseload. Science classes will be demanding, so find classes that can balance out the workload and will get you As without putting in too much effort. It'd be a plus if you actually enjoy this "easy" class, but sometimes it is what you gotta do to save your mental health.
3. Join some clubs. In the end, your ultimate goal is to stick to one or two clubs and climb to the highest position as possible within that club. Find the clubs you like, shoot for leadership positions in the years following.
4. Don't sweat on the idea of graduating earlier. If it works out for you, then that's great. If it doesn't, you gotta adapt to it. If you are sacrificing your GPA or too much mental health doing this, I don't think it's worth it.
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5. Go have fun! Attaining high GPA comes with sacrifices, but I think I would've gone insane if I didn't even go to a singular party lol