Check out the Pronunciation Check feature on my site to help you discover what types of words you are mispronouncing. First, click on a link to either the BBC or Voice of America and listen to a news story of interest to you. Read along with the transcript a few times. Then record yourself reading the transcript using the recording tool on the page. Play it back a few times to listen to yourself.
In addition to helping you improve your pronunciation, recording yourself helps you with your speed and intonation. Listen to the story you chose a few times, and compare how quickly and accurately you read with what the reporter says.