There is usually one thing we see or hear that sets the process in motion. In a combination of our expectations, and evidence, we latch onto something and the story begins to build. This is like the seed crystal in a super saturated solution. Suddenly all the evidence crystallises around it and it all becomes "clear". It is like a fractal forming around the initial pattern and each new spiral of coherence reinforces our emerging understanding. The meaning of this insight is simply...
Take care of what you see, take care of your first impression, it will determine the development of the whole episode. It will also influence the development of your unfolding character.