I Need To Learn How To Speak In English

[b]I need to learn how to speak in English.[/b] I think my English writing is somewhat decent enough but when I start talking in English, I get all tongue-tied and find it hard to speak. I stutter and stumble upon words even though my mind could think in English without the need to translate my native language into English. And most interviewers on my country uses English as the medium for communication...
What to do.....