My Desire To Learn!!

I always wanted to learn whistling. Not the ordinary one that we do for humming songs. That I had learnt with much difficulty and now I feel I am perfectly ok with it. But I always wanted to learn the whistling that produces much louder noise. We do it by folding our tongue. I like to learn it but never comes for me. Its so difficult. Is there any easy method to learn that Whistling? So that next time when I go to theater or to trips I too can whistle and make others astonished with my whistling. :-)