I'm a combination plotter and panster. I come up with a basic plot and list of characters for my stories, but the scenes often take a different path than I envisioned when I actually write them. Character's come to life and flesh themselves out as I type. It's kind of neat to watch.
Of course, I have to be flexible. When I start writing a particular
interaction, I sometimes realize a line of dialogue or character
reaction is implausible and have to change course. At other times, the
research alters something about the scene or a character's backstory.
It's fun and interesting at times, frustrating at others.