Right now, have as much fun and spend as much time with family/your SO as physically possible. Also, if you think you know what you want to do, go shadow to make sure. Being set on a specialty early on is viewed as silly, but it can take a lot of pressure off. I want to do rural Family Med- med school is hard, but I'm working hard because I want to be a good doctor, and that's infinitely more sustainable than working to get a higher score then the guy next to you by memorizing one more enzyme.
Once you get in- have perfect grades, a crazy high step 2 score, glowing letters of rec from outstanding attendings with connections in your specialty, and publish as many high-impact articles as possible. Oh, also be working on your clinical skills constantly in preclinical so you can honor all your rotations and crush your aways. Oh, and start a nonprofit in your copious free time that brings clean water to communities in need around the world.
Knowing "what" to do is simple. Actually pulling it off is wild. I'm a high B/low A student working well over 80 hours a week, and I'm not that involved. For me to do the above flawlessly I'd be working like 120 hours a week and hating my life. But I'm also not as smart as most med students haha I just really know how to study and I'm a workhorse.
MOST IMPORTANTLY- learn what YOU want, and plan accordingly. If you want to do internal med at a community program, why hate your life for 4 years? If you want to do MOHS surgery, better start maturing AnKing now haha. (kind of kidding, kind of serious).