It really depends on what your interview is like. I think it is always best to dress business formal. You can find guidelines in the following web site.

Here is why I say dress business formal: you can't lose with it. If you see that the situation is business casual, then you can always take your suit jacket off. You always want to look sharp. Here are some tips:

1. Get an adult haircut
   1. This means look professional and not like the 6th Beatle.
   2. You want to get a haircut about a week before your interview. This will allow your hair to grow out a little bit and it will let you look sharp but not rigid.
2. Use conditioner
   1. Nepali men don't tend to use conditioners. Sometimes, it's even more prevalent to use the soap. Don't be lazy. Get a proper men's shampoo, and conditioner. This will prevent from looking, for lack of better words: छ्याकर्याक्क
3. SHAVE!
   1. A clean shave is a must
   2. Here are instructions from this funny but helpful video on proper shaving techniques.
   3. If you are curious about what razor is the best, I use the Gillette ProGlide Fusion. They give me the most "सटासट" shave
4. Wear a nice suit
   1. Hear me out on this: many of us neglet the value of a fitted suit. It may be slightly more expensive, but trust me--you will look and feel 100x better. Plus it's not as unaffordable as you may think. You can get one at Burlington Coat Factory or Joseph A. Bank for <$200 sometimes. Joseph A. Bank sometimes even has a "Buy one get two free" sale, which I took advantage of once.
   2. Wherever you buy a suit, here are some of my suggestions:
      1. You want to stand out on your one-on-one interview, and not when you are going on a group tour. This means you need to be as not-standing-out as possible.
      2. Wear a black suit
      3. Wear a white shirt
      4. Wear a solid red tie. I understand the value of individuality, but you want to impress the admissions officials during your personal interview and not distract them.
      5. Wear black formal socks (do NOT NOT NOT wear white, or athletic socks. White socks with black pants is पखे and if you wear black socks that are intended for athletic events, then when you sit down, the socks will probably ride down. You don't want interviewers to see your legs. That shows sloppy dressing.
5. Wear nice shoes
   1. People look and judge your shoes. It's a fact. Some may not care if you are wearing sloppy shoes, but the point of an interview is to highlight your personal qualities and not have distractors like a bad haircut, or non-polished shoes.
6. BE ON TIME
   1. Be an hour early to an interview. I'm Nepali so I understand. If I target to be there an hour early, I will only then be there about 20 minutes early. There's a saying in the US Military: "If you are early you are on time, if you are on time you are late, and if you are late, it is unacceptable". Abide by that that motto!!
   2. It looks unprofessional when you are late. So remember: it is always better to be early
7. BE YOURSELF
   1. You're Nepali, you have an amazing story of coming to the United States already, and your life is already interesting. Don't bull5h!+ to the interviewers. They see right through you! Be true to yourself
8. Do your homework
   1. Every researcher thinks their research is the best. If you want to be in with an interviewer, you must do your homework beforehand. This means reading up on the topic and the general research. You can probably find that on the University's web site.
9. Relax
   1. If you are too nervous, that serves as a distraction as well. Best way to relax is to think about a happy place. I always think about a nice relaxing view. Do whatever works for you
10. Practice your interview
    1. Your college or university most likely has a career center where you can schedule a mock interview. If not, you can probably contact a local library and ask for interview resources. If that's not available either, you can go to your City's Workforce Development and ask them if there are services like that available. A mock interview is always a good way to prep for the day of. If you know answers to common interview questions like "What is your major strength?" "What are your major weaknesses?" "What is your research focusing on?" boosts your chance to not freeze up during the interview
    2. Find questions about the program that you will probably get to ask. This is the time to see if the program fits for you as well. You don't want to be stuck in a program that you want nothing to do with

I also use the following resource: The Pre-Interview Ritual

Hope that helps! Always treat an interview with seriousness. "First impression is the last(ing) impression"