I just go by reviews, usually from people I know. The only real difference between AA/A and Indie titles now really is marketing budget and size of team. Not much else is different. You also run into issues about what counts as indie now: it used to mean without a publisher, but it seems to have morphed into ‘a smaller company.’

But yeah, just look up reviews. Games like FTL, Hades, and so on tend to become known by word of mouth.