Compare the descriptions provided in your school's course catalog. The course descriptions will tell you what the course will cover and provide you with a decent idea of what to expect. These descriptions are typically a one paragraph summary of the course that give you a snapshot of each of the major curriculum areas covered by the course.
Search for courses using an online course comparison system. Many schools have these available on their websites, although it can take a little work to find these on some college websites. These are usually called "course equivalency guides" or something similar. Other websites and online tools are available to students in particular geographical locations. For instance, students in Texas can use the Texas Common Course Numbering System. This website allows you to search Texas colleges and universities by institution name, common course numbers between schools, community college course numbers that are comparable to university courses and by all courses common to two different institutions.
Ask other students who have taken the courses already. You may have to gain the input from several different students before you get an accurate picture of each course, but this will help you understand how the courses compare from a student's point-of-view. Some colleges and university dorms and social clubs (sororities and fraternities) also keep a file of the types of assignments that professors typically assign. If you have access to one of these, compare the assignments and grading of previous assignments that have been kept on file.
Request a syllabus from each professor or download them online. If your school does not keep an online version of the syllabus offered for each course, sending an email to the professor that teaches the course will usually get the task accomplished. Most professors are willing to provide you with a syllabus, especially if they only need to attach it as an email file and send it back to you. Compare the course description and outcomes on each syllabus as well as the evaluation techniques (quizzes, exams, papers, etc.), the course calendar and the required textbook. This should give you some idea as to which course will best suit your needs as a student.