By Mert - Dr.M.L.Bland, Arlington, VA, USA
One thing I often do is to draw a chalk line on the doorsill of the classroom and announce, "out there you can speak anything you want, but in here only English is allowed."
The simple act of creating an oasis of the target language in their lives goes a long way toward providing the immersion conditions which help crack the chains holding the two languages together. And if you can get them to use the target language to communicate (the essence of the CA), you destroy the illusion that the theirs is the only "real" language and all other languages have simply been created by their teachers to make life difficult for them.
And stock your oasis with as much authentic material as you can find: comic books, magazines, CDs, DVDs, paperbacks..... And drag in the occasional foreign visitor and let the students eavesdrop on your conversation.