Determine what field of study you are wanting to find university courses for. This can play a role in determining how you go about searching for the courses. Finding general education courses is somewhat easier to do than finding upper-level courses that might not always be included on regular class schedules.
Research schools to determine what schools may be best for your field of study. One way to do this is to simply consult the rankings lists established by "U.S. News & World Report" to see which programs are considered to be the top programs in the field of study you are pursuing. The publication includes ranking lists for many undergraduate and graduate schools. Narrow down the list of potential candidates based on factors such as cost, location and maybe even whether or not they offer online classes.
Visit the university's website. From there you can go to the homepage of the department you are seeking to take courses from. For instance, someone wanting to take courses in education at Oklahoma State University would go to the Oklahoma State Homepage (OkState.edu) and click the link for "academics" at the top of the page. Follow the links that lead you to the College of Education homepage. From there you can proceed to see what courses are offered in conjunction with the various degree programs offered by the College of Education.
Search for courses using the university's search engine form. Most colleges and universities have a Google search tool or some other type of search tool on their main homepage. If you are unable to locate classes by visiting the departmental homepage, you can conduct a search for "course catalog" or "courses in education"; this will likely take you to a link with course offerings.
Call the university registrar's office. If you are still unable to locate courses on your own, they can walk you through the their particular university's website to find the course offerings, or they can send you a course catalog for the upcoming semester. Most will be willing to do this if you simply ask!