Well, I think it depends on how you learn. For example, I know most college students don't read textbooks, but I don't feel like I've mastered the material if I don't read at least part of it. You're just going to have to figure out how you learn best (and you may find that different techniques work best for different classes).
However, if you prefer to watch lectures rather than reading a textbook, I'd recommend YouTube (e.g., Tyler Dewitt's general chemistry videos, Bozeman Science, Crash Course, etc...), Khan Academy, and any resources that your professor provides or that go along with your textbook (e.g., we were provided access to Thinkwell's Chemistry lectures, MasteringBiology, etc...).
Don't worry about it too much! 🙂 I know that I personally did worry about it, but looking back, I had nothing to worry about. Most likely, you'll learn as you go what works (and what doesn't work) for you. In addition, your professors will probably be happy to discuss study techniques with you and your classmates - I know mine were very open about it, because they wanted us to succeed.
