11:45 PM, Monday March 9th 2020
You look over the submitted work. From what you see you then go look thru the lesson text to find the exact section that explains the errors they are making. You then link them back to that section, adding some useful comments of your own if you think that will help clarify.
For the earlier lessons specially, everything is on the lesson text. You don't really need to come up with critique as much as point them to the right lesson and section. If you know something that's not on the lesson text, then don't make it part of your critique either.
The creator has included and also omitted just the right things from lessons, and all that comes from years and years of experience giving critique to thousands of students. You shouldn't claim to know better when just starting to give out critique.