I would suggest reading books which use proper English, ones that stay away from slang or ones that rely heavily upon regional dialects (but, this will be hard). Examples of good books would be: A Tale of Two Cities by Charles Dickens, The Miracle Worker by William Gibson, and/or Call of the Wild by Jack London.
It would also be helpful to watch English/American television with English captioning turned on. By doing this, you could both read and gear the words pronounced at the same time. Also, some books have been recorded to audio and you could use the audio while reading a book at the same time. This would deepen your understanding (and ability to identify words and say them properly).
(You may have many more suggestions if this post can be moved to the Discussion Board.)