For me, writing is like driving: I like to know my destination before I begin the journey. I like to outline. I like to have my title, even if it's just a working title, and I like knowing the ending. Any or all of these things may change along the way, but at the beginning I have an idea about where I am heading.
Maybe I start with a premise. Someone does something, and there are consequences. Maybe I start with a character in a situation, and the character drives the story.
Plot at its most basic is the orderly progression of action and reaction. The characters drive the action, and to be believable the characters and events should be grounded in recognizable reality.
What about fantasy and science fiction? They may share social structures with ones we are familiar with. They may have characters who are like us, but with special powers and characteristics. They may have situations in fantastic worlds, but be inhabited by beings we recognize. The language may be created by the author, but the meanings are ones we are familiar with.
I enjoy the creative process of having my characters in a world I control. Do they change along the way? Absolutely. Don't we all?
Let me know who your favorite characters are, and your favorite stories.