Although I love movies I seldom use them in the classroom. The biggest problems are that the language is normal or even above normal (flavored with special accents that I have seldom come in contact with in my 20+ years around the world, or peppered with the vocabulary of special interest groups of people like maybe hip-hop). I have few real advanced students who could understand 80-90% of this, most of mine are upper or lower-intermediates.
I buy into Krashen's input hypothesis which holds that the learner improves and progresses along the 'natural order' when he/she receives second language 'input' that is one step beyond his/her current stage of linguistic competence. For example, if a learner is at a stage 'i', then acquisition takes place when he/she is exposed to 'Comprehensible Input' that belongs to level 'i + 1'.
The second problem is time. Movies run to 90-120 minutes. If pauses are added that brings it to 120-150 minutes which in my situation is too long.
When I do show a movie I will preview the movie 2-3 times jotting down an outline of the movie, transcribing a few bits and also selecting certain sections to skip to cut the movie shorter. Of course, I also try to find the script on the Internet but seldom have success for the movies I have shown. But I do try to create some sort of hand out for the students to emphasize points I want to teach.
The bottom line has been that that they can take enormous amounts of time trying to prepare, show and teach from a movie.
Later I will discuss some great ways you can use movies.