During PS2, companies that come for investment banking seek only B3 students. So, if you are not in economics, tap into some contacts or alumni. People in corporations are really excited about BITSIANS. So, this job seeking in investment banking can be less tiresome due to the BITS tag.
A problem that I faced on entering this sector right after my undergrad degree, was that all my peers in the firm were either MBAs or had great work experience, which is the usual way to get into the sector. So, it was a little daunting to be amongst the more experienced people, but with time, I became acquainted with the culture