I'm an Indian student in Ontario, Canada. I want to travel to New York to meet some friends, but I do foresee having to travel to America to attend conferences and maybe do some fieldwork. Am I better off applying for a tourist visa and using it for both purposes?
The US has two visitor classes: B-1 for business and B-2 for pleasure. Almost all visitor visas are issued as combination B-1/B-2 visas.
Single purpose B-1 or B-2 visas appear to be issued when there are different reciprocity considerations for the two categories of visitors, and that varies by country. India does not have different reciprocity for the two categories, so the chances are high that your visa will be issued as a B-1/B-2 visa even if you ask for just a B-2 visa. I suppose it will not harm your visa application to say explicitly that you would like to have a B-1/B-2 visa if possible, because of the likelihood that you will want to attend conferences in the US in the future.
I would avoid mentioning fieldwork, since that could cause the visa officer to inquire about the potential nature of the fieldwork and whether it might require some sort of work visa. It would be better for you to consider that question only when you have a specific project in mind rather than in the abstract.
Edit: I just noticed the word "student" in the question title. You will not be able to apply for any sort of student visa without a sponsoring institution in the US, which usually means that you have to be planning to enroll as a student in that institution, so that isn't an option for you at the moment. So, to reiterate:
- The only option for your social visit is the B-2 or B-1/B-2 visa.
- You can use the B-1/B-2 visa for future visits as a "business" visitor; the B-2 visa does not offer this flexibility.
- The business visitor category is broader than its name might imply, and it does cover several kinds of professional visits that might arise for a student, including attending conferences.
- You will probably get a B-1/B-2 visa even if you don't ask for one.