Adventure of the Thrill
The thrill is the surprise.
And to keep that surprise, I traditionally limit research before every story because I don't want to destroy the Wow! factor of discovery. It keeps things fresh.
Of course, it helps to have a good hunch that the story will pan out. That's easy to figure out.
I call a friend and tell him the story I'm thinking of covering. If he says, "Need an assistant?" it will be a good story.
If he says, "Give me a call when you get back," it most likely will not be a good story.