Choose a course. If you are currently going to school, look through the graduate catalog available either online or in the campus bookstore. This will give you a list of courses, their summaries and the dates and times classes are held. If you are not a student, choose a college that is close enough to commute to and from classes.
Contact the graduate school admission office to determine eligibility. Depending on the institution or program, there may be stipulations on who is able to audit courses. Some schools allow any admitted graduate student to audit graduate-level courses, while others allow anyone willing to pay the tuition. Be specific about your desired courses, as some may be more popular (and thus more difficult to get into) than others.
Enroll as a student. If you are not already a student at the institution, apply for admission. The registration office will be able to tell you whether a Bachelor degree is necessary for auditing a graduate-level course. To apply, find the institution's web page and use the online application tools. You may be required to submit transcripts and prior test scores along with your application.
Register for the course. Once you are accepted into the institution or program, register for the course you'd like to audit. This may require contacting the admissions office or enrolling online. Be sure that you are enrolled as an "auditing" student. If this option is unavailable online, call the registration office for further instruction. Some schools will require the professor's signature for course auditing.
Pay tuition. Even though you are not taking the course to obtain credits for graduation, you will still be required to pay tuition. Most institutions allow you to do this online, although you can also pay in person or via regular mail.
Purchase your books and supplies. Most graduate-level courses will have a book or supply list on the course description or course syllabus. You can purchase these books in the campus bookstore or online. Having the appropriate books for the course will allow you to study the course material outside the classroom, and enhance your learning.