Make sure you inform your advisor of anything out of the ordinary on your tentative schedule. Have a list of questions ready. The better prepared you are for your meeting, the more your advisor can be of held to you. You also want to share your grades so far this semester with your advisor. How you are doing so far may have an impact on how you should register for next semester.
Every academic department has a list of the advisors assigned to each student.
Just go to the department housing your major program of study. The best source of information about a course you are having difficulty in is, obviously, the person who teaches it. See your professor during office hours or ask to make an appointment. When you go to see them, have specific questions in mind. Ask them to go over your previous examinations, look at homework problems you've attempted, or review your notes.