It depends entirely on the writer and the philosophy of the writer.
The best approach I've found is to just get the story onto paper in the first draft with the understanding that it's gonna be full of mistakes, plot holes, etc, and I'm OK with that. Second draft comes with the expansion of the story, details, ideas, motivations, and being able to try and make things more cohesive. 3rd draft is the removal of the weakest elements and maybe some tweaks here and there, but that's when I have someone generally read it.
A good way to break things down is to write the chapters in scenes, approach it from a movie lens perspective and write out the general flow and dialogue of the scene, then afterwards add in other details. Some writers get so caught up in useless description and don't actually add to the story. Another good thing to remember is the the three acts breakdown. Each chapter should have a general outline of start, rising action, finish, or a mini story within a story.
Characters are made interesting by conflict. It doesn't need to be 100% conflict all the time and it doesn't need to be extreme, but it has to have enough to help serve the characters, and it needs to serve the story. A human mind is a reflection of light and dark, good and evil, right and wrong, and this is what makes them interesting.
The other bit of best advice that I can give is, have a document that is your discard pile, because you can then cut stuff with impunity and go back to it and maybe use it for something else. But you must not be afraid to cut something if it doesn't work, there is no point in being precious about these things.