If you are thinking of taking a course at another institution (either study abroad or a summer class) while you are a Columbia student, then you will meet with the study abroad advisor in the department of economics. Before taking the course, you should meet with the study abroad advisor and discuss what classes you consider taking. You should bring with you either syllabi or course descriptions of the classes to that meeting. At that time, you will receive preliminary approval for those classes. When you return to Columbia after taking the class, you will again meet with the study abroad advisor to get final approval. To receive final approval, you must bring a syllabus and examples of your coursework demonstrating that the course was equivalent to its Columbia counterpart. You must get final approval in order for your transfer class(es) to be credited towards your major or concentration.
If you have already taken the course, then you will first meet with your CC or GS advisor. He or she will give you a memo (also available online on the Transfer Credit page of the department website) that outlines what materials you need to supply with your application for transfer credits.