Just the same as Nick said, really! Although if you want to practise, I suggest you watch videos in English and try and repeat what they say to get the correct pronunciation ^^

Practice practice practice ;) The more you try, the better you'll get. No real shortcuts there, unfortunately.

Perhaps, you will find useful videos here http://www.engvid.com/topic/pronunciation/ They describe some ways to improve pronunciation.

In your practice, make sure you are following good, clear examples, and that you are getting feedback. Otherwise you're just repeating your mistakes. Some members have recorded themselves and posted the link here for feedback. Perhaps you could do the same? (I recommend vocaroo.com - you don't need an account.)