The sad fact is that there are no truly "original" stories anymore. I've had instructors that say there's only like five base stories out there. Every story, once boiled down to it's essential functions, is one of those five types. (i.e. the strange comes to town/Cinderella)
Now, that's not all bad news. You, the writer, get to retell these tales in whatever fashion that you'd wish. The "originality" of each stories comes from how the writer writes it, the characters, the setting, the prose - all that jazz.
And that "originality" isn't something found in a magical formula - it's something that you find on your own, through your own writing, through practice and exploration. In writing, you'll find ways that you like to say things and ways that you don't, and from all that writing you'll find your "voice" with which you'll write. Luckily, each book makes that voice clearer. I mean, I was on my third novel when I figured it out.
As for quick-answer plot twists, I don't really have any. Once you start mapping out your story and you characters, those plot twists will start to reveal themselves, or hint at themselves. You might have to get through a first draft before you see those twists, too.
The novel that I'm finishing out now was set aside for a few months because I thought I'd "ended" it, but it didn't feel right. Then, while in the shower, I had the idea to mash it with another story idea floating around, and it worked.
So...sorry for the long post. But good luck!