Mostly, I look at the story as a whole: -What does the author want´s to tell? – What are his/her characters like? – What is most important for his story? – How does he/she want the character to change.
Then, I look at the chapters, sentences, what´s happening, does the author really wrote about, what he wanted to, could there be another way to brite a sentence, et cetera.
And after all of that, I look at grammar. I think an author can´t be bothered how to exactly write a word.
I bring my thoughts and doubts as well into the story but it´s not my story, so no one has to do what I say. 🙂
For myself, for example, I need some butt-kicking people, who say: “Go on writing now, Duh!” It all comes out to hard work. And a lot of people are afraid of that.
But writing should be fun as well. Cake.