The Idea Seed
The old adage of "nothing comes from nothing" is a very true statement and especially true of telling a story. There has to be some kind of foundation, some kind of bedrock to build the rest of your production on. Have you noticed how successful Pixar is at creating animated films? Is it because of the eye-popping visuals? The celebrity voice work? The stellar sound mixing? All of these things contribute, but it's attention to the screenplay before one frame gets created that has put Pixar at the top of their game. It's one of their creative principles that sets them ahead of the pack.
What about before the script? What's the egg to this chicken? It's nothing more than that nebulous thing that no one can pinpoint an origin of: the good idea. It's that spark of thought that happens in the strangest and most unpredictable of places (for me, the shower a lot of the time), but when it comes, you feel like a changed person. Your mind races and a skeleton starts to build over that tiny synapse of inspiration.
For me, a good litmus test is "am I excited the next day about the same thing?". If not, the seed is cast away (or archived in a notebook), making room for the next big thing to form a story around. It will happen, I can't seem to control it, and I feel driven to take those ideas that really excite me and get them on a screen somehow. It's the same with all creative types no matter what the medium. The important thing is that when those good seeds are planted, that they are nourished and allowed to grow. Nothing is more sad than a dead sapling that could have been a great tree. Or movie.