Here's my preferred way:
1. Get some movies in English.
2. Before watching, find the subtitles on the internet, write down the words you don't know.
3. It's a shameless plug, but I suggest my software (available at
wordoholic.com | memorize foreign words in (almost) no time ) to memorize the words.
4. Watch the movie with subtitles OFF and catch the words you've learned.
Generally speaking, I'm against subtitles as you tend to read them narrated instead of watching a movie.