(OT for off topic, as this is not a writing prompt, but a discussion post!)

Someone commented on one of my responses on here with a sort of analysis of the story I wrote, pointing out a few things I hadn't even realized made it into the piece. Usually, I don't plan when I write. I don't consider what themes to put in, or what underlying story I'm trying to tell, or anything quite like that. I heard somewhere "write into the fog"; basically, writing without a solid idea of what you're gonna write or planning it out before hand, which describes a lot of what I do.

However, I'm curious to hear how you all do it! Do you plan the themes before writing? Do you think on it for a while and come up with specifics ideas, concepts, questions, etc to present in between the lines you write, as little nuggets of gold or Easter eggs for careful or curious readers to find or think about? Or is there something else you do, that's completely different from anything I'm talking about?