Like everyone has just said subtitles in english would be very helpful but also try doing a little research before watching the movie. If you know, generally, what the movie will be about then you can pick out key vocabulary that will be crucial to understanding the film. All of the times you can figure out the key words by the genre that it is in, this is very helpful in at least getting the jist of what people are saying. Also take in to account that many films will have different accents depending on where the movie is suppse to take place, some accents are harder than others to understand. Hope this helps.

Try to watch movies with subtitles in English, so while hearing them speaking, you can read what they are talking in movie, after a while you can get the fast talking I guess ^^

If watching on a PC or media player you can download subtitles for the movie - in your language or in English. http://www.opensubtitles.org/en/search