In my brother's and another relative's case, New Delhi Embassy did not ask for police clearance. They ONLY asked for Passport Clearance Certificate. So you donot have to spend money on police clearance certificates. If your petitioner/sponsor did not provide Year 2011 Tax Papers (FORM 1040) to NVC, then you need to take these papers with you to the interview. If there is an additional sponsor, then you also need YEAR 2011 Tax paper's from the co-sponsor.