For intermediate to advanced English learners; choose a TV series that you enjoy watching, preferably drama, and focus on an actor or actress that you would like to emulate. You should listen in English and read the subtitles in English, too. They probably won't match, but that's okay; you'll learn two ways to express the same idea. You'll need a good dictionary for this exercise. I recommend wordreference.com.
Watch each episode 3 times: the first time watching continuously to understand the context, the second time stopping often to note down new vocabulary and idiomatic phrases and the third time watching while repeating the phrases aloud. It's important to focus on learning phrases and not individual words.
Try to use this new vocabulary as soon as possible by telling someone else what happens in the episode. If you can't find someone to tell, this is where a private English teacher can be helpful. He or she will not only listen, but will listen carefully and correct you.