When you're critiquing a story, there are lots of possible things you can comment on. When you're looking at one of your own stories with a view to improving it, there are lots of things you can change. After thinking about it for a while, I decided there was what you could call a hierarchy of changes.
If you're asking someone to comment on your story, it's often helpful if you can specify what sort of level of critique you need. Do you want comments on whether the story works overall, or do you want line-by-line comments on the sentence level prose? Also, when you're revising a story of your own, you need to bear in mind the possible levels of change. It's not very helpful to spend hours polishing part of your novel at the sentence level if you're later going to cut most of that chapter. This is something I wish I had realised years ago. Until fairly recently, my idea of revising was sentence level polishing. Well, that's not quite true; I did hack stuff about, but often only after I'd spent time polishing it.
And here's some examples of these:
Overall story/novel structure: Changing things like where the story starts, e.g. deciding to start in the middle and then do a flashback to fill in the rest instead of starting at the beginning and continuing to the end.
Changing genre, or viewpoint or sex of main character: Deciding that the romance between the main characters is more important than the murder they are investigating and making the story a romance instead of a whodunit. Changing the story from third person to first. (Jasper Fforde did this with his first novel The Eyre Affair.) Deciding the story would work better with a woman as the main character instead of a man.
Order of chapters or events: Deciding that the story would make more sense if event B happened before event A, rather than the other way round.
Cutting or adding a subplot or chapter: Simplifying the story by cutting a whole plot strand (e.g. removing the romance between the two main characters and concentrating on solving the murder) or making a too-simple story more complex by adding one.
Paragraph order: Deciding that it would be better to describe the ancient manor house after the detective enters the great hall and view it through her eyes rather than describe it before she appears on the scene.
Cutting or adding paragraphs: Realising that you described the ancient suits of armour all hung about with cobwebs the first time the detective went to meet the eccentric millionaire and you've just described them again. Realising that nowhere in the story have you explained the vital detail on which the plot hinges.
Sentence order: Altering the order of the sentences to make the prose read more smoothly or clearly.
Light pruning: Removing superfluous sentences or words, e.g. getting rid of excessive adjectives and adverbs.
Word order: Making sure the words in a sentence are in the best order.
Word choice: Making sure you have chosen the strongest verb or the most appropriate adjective.