Start reading novels! And non-fiction. And longer / feature articles in the New York Times, Wall Street Journal, Washington Post (or similar). Just start reading.
I'm a fan of the authors Doris Lessing (fiction), John McPhee (non-fiction), Pearl Buck (fiction), William Manchester (non-fiction), Thornton Wilder (fiction). I also love Agatha Christie (mystery novelist) - the books are on the shorter side and a bit "lighter," but she's always grammatically correct and on the somewhat more formal side, writing-wise, so it's good practice for language skills.
Find a TV series that sounds interesting to you and start watching it. Don't use subtitles, but find a website that provides summaries (or "recaps") of the episodes for that show (I like . You can check your understanding at any point in the episode or once it's all over.
I'm a fan of the recap site Television Without Pity (TWoP), which has closed down, unfortunately, but an archive of their recaps can be found here:
http://www.brilliantbutcancelled.com/shows/The shows can have very long recaps - an hour-long show could be 8 to 12 pages of text- but they usually offer a "recaplet" summary, just 3-5 paragraphs of the main points. I'd use the recaplets. The full recaps include a lot of commentary on the show, as well as the plot points themselves.
Or, if the show that you want to watch isn't on TWoP, just google the show's title with the word recap and you'll find something!