WHO IS SAYING WHAT TO WHOM is the essence of communication. Writing is just a way of making it asynchronous, i.e., you put it down in words on Thursday, and next Tuesday someone picks it up and reads it. Time-traveling, in one direction.
THE WHAT usually strikes one as the important element. And it is. If you think about it, what is it exactly that gets transferred from one mind to another?
THE WHY may be the place to start. Are you required to write? Or do you simply want to say something, and hope that the reader is interested enough to read.
ARE YOU CLEAR about why you write, what you want to say, and who is your audience?