I think the most important thing is not just going to class and reading the book, but whenever you have a question, it's absolutely necessary to speak to the professor. He's the one that knows the topic and he's the best one to answer the question.
See your TA's during their office hours and talk to your professors. The first semester here I sat in the back and was an unknown face. This semester I got to know my T.A.'s and professors and went to see them during their office hours. I feel more comfortable now and I think it's helped me do better.
Get help right away. Don't wait until you're doing badly in a class and have to catch up.
It's a good idea to get to know professors and T.A.'s. I've actually gotten to be on a first name basis with a couple of my professors. They want to help. Reach out when you need them.
The only way to get to know a professor is to sit in the front row of class every day. Then go to her/his office hours. Also, get to know the T.A.'s. You spend more time talking with them, and they know you well enough to help you.