I am both a producer and writer, even, heaven forbid, an occasional director. I have noted what many writers state that you should NEVER share an idea with ANYONE until you have a signed NON DISCLOSURE AGREEMENT. I have to caution aspiring writers that this advice is not going to work with many production companies who will tell you politely to shove your idea up your NDA! Check out who you're dealing with, and if they have a good reputation and have been in business a long time they usually are not thieves of ideas. Of course before you submit anything register your written material in the most effective manner, which is usually the WGA, which is fast, easy, efficient and reasonably priced. As a production company if someone comes on to us with unsolicited material we pretty much say no automatically unless we know the person submitting or his agent or lawyer. Otherwise we don't want the potential hassle, and if he / she came with an NDA we would say thanks but no thanks.
Hey Tony! Agreed - no producer, director, agent, firm will accept any work if there's an NDA attached to it. Writers can protect their work by having it registered with the WGA (as you mention) and/or having it copyrighted. Writers - focus on completing your idea and presenting a written masterpiece ... get it registered ... and let the powers that be do the rest.
We are in agreement Jim, but I would add that the creation of the written work is creating the copyright, all you can then do is register it, as we both mention.