Best resource to write a screenplay?

I have an idea for a screenplay that I really like, but I’m having difficulty organizing and fitting the details into a successful structure that flows. Is there a website or a book that is best to use to help me with the mechanics and polish of making a great screenplay?

I think of the course that Nick Cage takes in Adaption, which infuriates his twin for it’s canned, generic application, yet still helps them build a rich narrative. Granted, I’m no Charlie Kauffman, but I think you get the point.

Thanks.