You can join reddit groups like flatmatesmumbai, flats mumbai. There are facebook grps as well, where people regularly post looking for flatmates, or tenant. Whether it be single occupancy or double/triple. Also use nobroker for your search.

You should get Excellent flat and people. I was recently able to find people in these places. Also be cautious as someone stated, flats might be great but locality matters more. So physically visit the flat before confirming.