Read English literature (both British and American) written after the 19th century. Literature published before the 19th century may not prove as beneficial to you since it includes a lot of Old English, such as thus, thou, thine, and other phrases that are not used in modern English. A good anthology like "Norton's Anthology of English Literature" will provide a broad range of works. According to Alex Case at UsingEnglish.com, read books with lots of dialogue because it is more like the language you want to learn to speak.
Read literature out loud. This will help develop both your narrative and conversational skills. Also, seeing the language in print will help you understand sentence structure. In addition to reading literature, also read English grammar books and visit online grammar sites such as GrammarBook.com.
Watch public service TV channels such as PBS and the BBC on a regular basis. Many of the more popular entertainment and news channels feature programs that use slang and incorrect English on a regular basis, which will not help you. However, PBS and the BBC tend to adhere to the rules of the English language, so watching their shows may improve your command of the language.
Listen to public radio stations such as NPR. Like public service TV channels, NPR holds fast to the rules governing the English language. While it is not always convenient to watch TV, you can listen to the radio (or even listen to TV) while brushing your teeth, washing dishes, driving, or soaking in the bathtub.
Repetition is the key to fluency and spontaneity. In other words, practice. Read literature over and over until the words flow easily. Videotape shows on public TV, then play and pause them so you can practice what has been said. Try to mimic not only what has been said, but also how it was said, which means paying attention to the tone and tempo of the phrases. According to SpeakEnglish.com, "You should practice speaking out loud until your mouth and brain can do it without any effort." Once you are comfortable with the English language, you will have the confidence to speak fluently and spontaneously.