I know for a Patent, you need to file with US PATENT OFFICE.
I'm on my phone or I would google a link for you.
The website is very informative in regards to what can and can't be patented.
Not sure this helps at all, just what I know.

 

as long as your work has a time stamp that can show you were the original creator you should be fine, I think.
The official website has some good info and a FAQ

http://www.copyright.gov/circs/circ1.pdf

 

http://www.copyright.gov/forms/

 

Email yourself a copy of each script, and (of course) keep the emails. Do it on several email accounts if you have them, to spread the risk of losing one. Then you'll have proof of their existence, intact, on a certain date.

Remember, though, that you may copyright the scripts, but you can't copyright an idea. You may send in your scripts and the producers of the show may not use them, but may springboard off your ideas.

It's an unavoidable risk, though.

 

If it's the same as with movies, you may have to first register with the Screenwriters Guild.

 

Screenwriters Guild has nothing to do with copyright, though it may (or may not, I dunno), have something to do with your ability to market the work as a practical matter.