First, in order to pursue psychiatry, you'll need to make sure you take all your pre-med courses and meet all of the requirements for medical school. That is not true if you are pursuing a career as a clinical psychologist, in which case you'd have to make sure you take all the necessary classes to get into graduate school in clinical psychology (and I'm not sure what those requirements are)

As to your questions regarding psychology courses as an undergrad - I'd say that any psychology courses you take are worthwhile if you are interested in becoming a psychiatrist. I really only took a few psychology classes becaues at the time, those were the only courses that seemed interesting to me.

Generaly psychology will definitely give you a good basic perspective of the field of psychology; however, it doesn't necessarily relate much to the general practice of psychology / psychiatry or give much insight into how someone uses the knowledge in the clinical realm (at least that's what I remember from my pscyhology class in college).

As for social psychology, I'm not really sure how relevant that will be, as I never took a social psychology course. I would imagine that there would be some aspects of that course which would deal with interpersonal relationships and personality related to that - which would probably give you some additional perspective on psychopathology.

The psychology courses I took in college included general psychology, brain and behavior, and drugs and behavior. These were courses of interest to me because of the topics as well as the professors. I didn't have any interest in the other psychology classes at that time, but in retrospect, I think it would have been useful if I had taken more - as the curriculum in psychiatry residency programs is actually quite different from the general theoretical material you learn in the college and probably graduate psychology classes.

If there are any classes that deal with psychopathology or treatment modalities, those would give you the most insight into what a psychiatrist will deal with. I'm guessing that college level psychology classes in general won't give you that much perspective on this stuff though. For me, I think the brain and behavior / drugs and behavior classes were the closest to psychopharmacology classes we had as undergrads - which game me a good foundation for understanding the biology of medication management.

I don't think you really get a glimpse of what psychiatry is really like until you do your 3rd year medical school rotation in psychiatry. And even then, the rotation is usually fairly short, and you will be heavily biased by the particular location you do the rotation and who your attending physicians and residents are you work with.