If one were to apply for business/finance major, what kind of extracurriculars would look good to show interest in this field?
Likewise what about if one were to apply for international relations/public policy, what kinds of extracurriculars would look good to show interest in this field?
Also, would being part of a nonprofit organization look good for all these types of concentrations?
Rather hard and biting but there’s wisdom to this first post (note paragraphs 4 & 5):
It’s not what you DO, it’s who you ARE that will get Harvard’s attention.
Harvard doesn’t have a business/finance major so there are no extracurriculars that would help you show interest in that field.
You could, however, join a third of the student body and major in economics 
T26E4 is right. It’s probably crushing to hear that, but on the bright side, you can still change. Find out what really interests you and start pursuing it/them. Being part of model UN doesn’t make you interesting. Why you joined model UN does. 
@CollegeAdvice347 - I believe about one eighth of Harvard graduates earn degrees in Economic, not one third.
@BldrDad I was joking about one third. Here are the actual numbers.
http://handbook.fas.harvard.edu/icb/icb.do?keyword=k104674&pageid=icb.page673468
Likely a bit more if FAS included joint concentrators. 
@CollegeAdvice347 - I commented because it’s likely that some readers would take this as fact. The number of concentrators (577) would be the combined sum of sophomores, juniors, and seniors, and Economics does not allow joint concentrations, so that’s it (about 200/year).
@BldrDad Apologies. In regards to joint concentrations, It seems Harvard Economics has changed since I was there.
@CollegeAdvice347 - Joint concentrations sound like they may be more trouble than they are worth - far more difficult to achieve than a double major at other institutions, as both departments must allow joint concentrations, approval from both departments is required, and an interdisciplinary thesis is normally required. My daughter has investigated the possibility of a joint concentration including CS and apparently it’s going to be a hard sell to convince them to approve it.
So let me revise the first question: If one were to apply for Econmajor, what kind of extracurriculars would look good to show interest in this field?
and any answers to the other 2 questions also originally posted? thx.
bump
All students apply to Harvard College as Liberal Arts Majors and then decide upon a major (called a concentration) during their sophomore year.
The reason Harvard, and other colleges, ask you about your “intended major” is to gauge your interests. However, as more than half of all college students change their major at least once during their 4 years of college, Admissions cannot use your “intended major” as a recruiting tool because the data doesn’t directly translate into what major a student will graduate with. Got it?
So . . as all students apply to Harvard as Liberal Arts Majors, it doesn’t matter what extracurricular activities you do, so long as you show a commitment – measured in years not months – to something.
The idea is that your long term commitment could be translatable to something else in your college years and beyond. Your commitment – some might use the word passion, but I think that word is overused and misunderstood – could be to hopscotch, chess, theater, a sport, debate, a job etc – it doesn’t have to relate to your intended major. In fact, I’m willing to bet that most students admitted to Harvard don’t have EC’s that are related to their “intended major.” Read this: http://www.huffingtonpost.com/marjorie-hansen-shaevitz/extra-curricular-activities-college-admission_b_3040217.html
That is true for a student interested in Econ, as well as bio, math, chemistry, history, english or anything else! So, do what you love! And don’t worry about doing something to show your interest in Econ, as that is NOT the approach you should be taking with your college applications, as it’s backwards thinking. You are trying to guess what Admissions Officers will like when viewing your application – and from past experience successful students admitted to Harvard and all selective colleges don’t work that way. I think that was what @T26E4 was trying to tell you in post #1.
I saw someone else post who is interested in business/economics. A few of his extracurriculars included, starting and maintaining a successful and profitable business, an internship at a bank, an investment club, and debate. Those seemed like some good extracurriclars that show interest in the field.