0 balance but certain branch employees want you to keep certain balance to issue specific type of debit cards. And autosweep feature (if you open Savings Plus/SB Plus account) requires at least 35K so balance above 25K goes for sweep.
In metro, it used to be 300 for non cheque book and 1000 with cheque book as mab for normal savings account. There were lot of complaints about deduction of non maintenance charges and some years ago they made it 0 as an offer.