Before writing any story, it is of extreme importance to assign a general plotline. Here, the author might not grasp how things would turn out. Quite the contrary, the writer will be as bewildered as the reader with how things could go on in the imaginary world. For that, one must not assume to comprehend how every detail will be sorted. It kind of just flows.
However, there is one point that is crucial, and which could be overlooked by many aspiring writers: Character Dynamics.
What's that? One might ask.
Character dynamics are the ways your characters interact in the imaginary realm. Before writing the actual story, what I usually do is that I stumble upon fitting characters that are evaluated for the position I want. After that, I place them in a separate experimental realm to observe their behavior and to pin down whether they are suitable or not. It would then be interesting to discover their backstories and anything that might have led them into who they are as a lovely addition to the whole plot. This job, as one might expect, is notably enjoyable.
After that, I place more than one character with them to witness their dynamics. "Is this what I want to see in my novel? Is this what I want to portray to the reader?" I question myself. If yes, then I would go along with it. If not, then I would dismiss the character and hunt for someone else in the archive.
One might be impressed with what the characters could give out in these fields, and this points to the importance of such a deep study of character dynamics.
On various occasions, I would attempt to place myself with a premeditated character in my mind. Countless times, the way they react is agressive. I do know however that fundamentally speaking, evinced characters are nothing but a manifestation of a thought or emotion I happen to have deep in my unconscious mind.
The ability to exhibit these thoughts in this style, and to properly convey what they feel like accurately, marks the talent of the designer.
The more you could make your reader "feel" with what these subjects are going through, the better you are doing your job. This, in itself, is one remarkable beauty of writing. It is enough for me to touch that as a reward for my work, and I would want nothing more.