I've always approached movies by first asking myself: "Ok, what am I watching?"
Science Fiction?
Historical Drama?
Fiction?
Etc., etc.
Once I know what I'm getting into, I go in with that frame of mind.
For example, if I'm watching a Godzilla movie, I just go in and have fun and laugh at the BS. I don't look for inaccuracies.
But if I'm watching stuff like Black Hawk Down, Warfare, or Platoon, I do look for military accuracy. Not so much on Rambo, Commando, and Van Damme BS movies.