B1/B2 Renewal - 221G (India)

My B1/B2 visa expired this month, it had a validity of only 1 year and an annotation saying 'clearance received dd-mm-yy'. So I did qualify for an interview waiver, and had submitted my passport to Bangalore VAC for renewal last month. Today I received my passport back with a white paper, asking me to attend an interview in Delhi Embassy (no tickmarks on any of the other 221G boxes). I need advice on what all documents should I carry with me to be on the safe side. And, what kind of questions should I be expecting. I travel to US only for business meetings, conferences and have been there thrice in the last year (each trip of max 2 weeks)