I find the Guardian film reviews useful for this. If they give it 5 stars and go into raptures about it, then DO NOT WATCH THIS FILM UNDER ANY CIRCUMSTANCES!. It will invariably be Swedish or Icelandic, with subtitles, possibly in black and white, feature people mumbling incoherently, long, lingering arty, yet pointless, camera shots, it will be spirit-crushingly depressing, and absolutely nothing at all will happen! Then it will end, and you’ll turn to each other and say WTF was that all about?!
It took me about 3 films, each of which seemed about a fortnight long, to realise that they’re just all like this