When I do a crit, I read the chapter(s) through twice. The first time I make initial impression notes, things that stand out to me as if I’d picked up the novel off a bookshelf at a store.
The second read through I go for detail. I point out phrases or sentences that work or don’t work for me. I show where things don’t make sense to me, and places where I have “aha!” moments (like when something was foreshadowed a few chapters back and I realize now why it was important).
I make comments on how well a chapter or section reads – does it flow, is the pace good, do I think the author is achieving what they’ve set out to do.
I always take into account the writer’s requests – and I do point out grammar and spelling errors, but I don’t make a big deal out of it.