I have over six ideas for potential screenplays. I have many things figured out but I'm struggling in taking the first step. I'm afraid that if I start to write it, I'll ruin this great story that I have in my head. What's the best way to start writing (I've done some outlines and written and re-written the stories)? Also, upon finishing the screenplay, do you need to get a copyright for it?
Let's take copyright first. You don't need to copyright a screenplay, but it's not a bad idea. Check out the website for the Library of Congress for more info http://www.copyright.gov/. But you absolutely should register the script with the WGAw, for $20 (http://www.wga.org). That's what the WGA uses to assess writing credits if the material gets made. And it proves you wrote what when. The only downside is that the WGA registration only lasts 5 years and the material is tossed. The copyright lives forever (well, 70 years), so doing both is fine.
But here's the thing: the idea itself isn't copyrightable. It's all in your execution -- that's what you copyright. Which is why you need to keep good records of who's read your script (people and production companies), what their answers were, that sort of thing. Keep a log for each script, register your work, and get out there and pitch it like mad. If no one ever reads it, no one will ever buy it. Risking having the idea be stolen is part of the game; protect yourself as best you can and don't worry about it.
The good news is, you'll have lots and lots of good ideas. Which kind of leads to the next thing: you have to risk writing some of them. The fact is, you'll never get better as a writer if you don't write. Don't worry about screwing it up. On the contrary, your first draft should suck. Give yourself permission to stink. That's the only way to beat writer's block (which I'm guessing you have, just from the way you said you wrote and rewrote the stories and outlines.) Again, no big deal, every writer goes through it. But if you're worried about being perfect, you'll never write.
The best way to start writing? Anything that works. For you, I suggest the double-whammy of setting aside 20 minutes every day that is sacred, non-negotiable writing time, and then letting yourself write any part of the script you want. Jump around between scenes, write your favorite scenes first, who cares? Nobody's grading you. Trick yourself into getting something on the page. Be grammar-free; misspell; write a terrible first draft. After that, you can revise to your heart's content and gradually make it better and better. And the thing is, you'll learn from each script, even each draft. So get writing -- not outlining, writing. And have fun!