Even the best students can't remember everything that is discussed during a 48 minute class. So, write down the main ideas that are covered in each class as well as the important formulas and tips that are provided. Notes allow you to review and soak in the information outside of class. No matter how dumb you may think a question will sound, chances are, there are other students in class who were thinking about asking the same question. Do your homework regularly.
Homework is assigned because it is a good way to reinforce what is taught during class.
Attempting homework problems on your own helps you to review the ideas and to more fully learn.