As authors, we have a lot of work to do before we start writing a story. From thinking of a concept to research to plotting and not to mention the most important task of characterization!
Authors have different techniques of developing their characters. When I started writing fiction, I used to develop my characters in a word document and it worked fine. However, over the years, I have moved on to excel sheets for filling in details of all my characters in my stories. I’m not sure why but I find that excel sheets work better, perhaps because I can see all characters side by side. This makes me not only focus on a particular character but also do a comparative analysis while I am filling in details.
Hope this helps, happy writing!