If you are absolutely certain that this is your chosen field of study, then you should major in psychology as an undergraduate. However, if you are not positive, realize you can still apply to a graduate program in psychology even if you only minored in psychology as an undergraduate. This way, you can major in something more generalized (business for example) and if you decide you don’t like psych anymore you’ll have a bachelors degree that can take you other places.

The course requirements to apply to different psych programs vary, but generally, you’ll at a minimum need basic psychology, psych research design and statistics.