It took a lot of research to pull it together, to obtain photos, and so on. Work on one article at a time and keep everything for it in one place. I have an attach case. Everything goes in there. Everything goes with me to the library.
Nothing can drift further than that case.
I start with the idea. For example, I just finished the April edition of The Upper Midwest Historian. I am now thinking about the October edition and what will be the feature article. Once I have the subject, then I narrow it down. For example, for the April edition the feature article is about the Civil War, not the whole war and certainly not every aspect of the war.