The quickest and easiest method of copyrighting any manuscript is to stick a copy in an envelope and send it to yourself, make sure that the date stamp from post office is visible and don't open it, unless you have to. As an extra precaution you could also get someone to read it and sign a piece of paper saying that they have done so and stick inside the envelope as well. I would suggest you invest in a copy of the Writer's & Artists Yearbook, there are two, one red, the other yellow, slightly differing names, you could also find them at your local library and they usually have a section dealing with film & TV. You can also get The Writers Handbook: Guide to Writing for Stage & Screen. I would suggest either you become acquainted with the film section in your local library or visit the biggest bookstore you can find and invest in a few books or at least pick up a few titles dealing with this subject. There are loads of books out there on the subject. May I suggest either Foyles or Borders on the Charing Cross Road if you live in London, or get the opportunity to visit?