Each course and instructor is somewhat different. Your instructor should give you a course syllabus, a description of the course with information on what you need to do to pass the course. Keep your course syllabus as the first page of your class notebook. This may sound somewhat compulsive, but a well-kept notebook can be a great help to you. Keep all your notes in a three-ring or other insertable binder. Everything pertaining to the course should go into the notebook, preferably in date order.
Taking class notes is another important art. You must be able to judge what is important enough to write in your notes. If you are too busy writing notes, you may miss something useful. If you have trouble taking notes, you should compare your notes with the notes of other students in the same class as soon after the class as you can.
If you need help or information (notes or assignments) in the course, your first questions should go to the members of your lab or study group. Next, ask other students in the class. Get the name and phone number or email address of the members of your lab group and other students in the class. Keep these in your notebook. Contact them when you need guidance about course requirements.
Some colleges or universities have teaching professors who only lecture and TA's (teaching assistants) who will do the "dirty" work of consulting with students in small groups, give quizzes, and grade tests. Most lecturing professors will stick to the material in the course, but, since the classes are large, do not take questions during the class. You need to rely on your TA for help in the class.
Some colleges and universities allow you to drop a course before the end of it to preserve your grade average. If for some reason you need to drop out of the course, give your instructor the courtesy of the opportunity to talk with you. There are some good reasons for wanting to drop out; you don't feel you have the background, you don't have the time to devote to the work, you have other turmoil in your life and can't expend the emotional or mental effort, your work schedule conflicts with your school, etc.