Usually when somebody wants me to go over a piece of their writing, they have a question about grammar, or they just want me to quickly “fix” it so that it’s readable. They are far less interested in learning how to improve the artistry of their writing than they are in getting it done, ideally as painlessly as possible.
I always come at a piece of writing with the reader in mind. What do they need to know? What are they likely to know already? Do they have the technical background to understand the scientific gobbledegook, or does it need to be simplified for clarity? Is there a story? How can we tell the story so that it is interesting? If we need to illustrate a concept or process, can we find a story that’s relevant to tell? Are there any photographs? Are there any interesting photographs? Are there any photographs of something other than the same technician standing next to the same very expensive piece of equipment that is in all the other photographs from all the other projects?
I have rarely critiqued fiction, at least for another person. I do keep a journal of most of the books I have read, and what I thought about them (only some of these reviews end up on Goodreads). There are some books to which I wrote love letters. There are some to which I wrote hate mail. And there are some that I only finished reading because mocking all their flaws was so much fun [0].