As far as study skills and habits, I recommend taking classes early in the morning (as early as you can handle) and grouped together, then you go straight to the library, and don't come home from the apartment until you've finished your homework. Plan on spending 8-5 on campus and you'll rarely have to be there longer than that. (Assuming you don't waste time on facebook, imgur, etc.)
Also, one thing that helped me immensely to have a "balanced" life at college was joining the Clubs that related to my career. Look up your school's Pre-Med society, join it, and then try to help out and become a leader within the club. Even being president will require, at most, 5-hours a week, but you'll accomplish a TON to prepare you for graduate school and get a tight-knit group of friends at the same time.
Last, I recommend reading this book. I've loved it and used it multiple times when advising students: https://www.amazon.com/How-Win-College-Surprising-Countrys/dp/0767917871/ref=mt_paperback?_encoding=UTF8&me=