For all the NDB aspirants:
1)Technically you can write the NDB on a tourist visa , it is not offered in India
2) Not telling the VO about your actual plan , might get you the visa but remember the world is a different place now , all tourists and any kind of visitors are very closely monitored now and it is actually very easy for the INS to find out what a person is up to while their stay in the US . So as far as possible try to be honest.
3) For the aspirant who wants to get a sponsorship letter from a sibling , actually this might work both ways , a close relative or sibling well settled in another country is actually a very strong reason for urself to be a potential immigrant , hence re think that option.
4) Many people do take up non clinical masters programs , but first do figure out your funding sources and remember that these programs might take up a lot of your time and divert you from scoring high on the boards
Good luck