Evaluate the student's ability to recognize the most disruptive error
Make sure you have an example of the most disruptive error and of the first sub-category from which you want to build your explanations. Ask the student to read the sentence to see if he can spot any problem. (You'll want to do a bit of diagnosing at this stage to find out what the student knows and how negative his attitudes are toward editing.) Sometimes, students, especially native speakers, are more likely to "hear" a problem than see it, so be sure to have these students read sentences aloud.
If the student can tell you how to fix the problem, have him do that and then go to the next example of the same sub-category of error. If the student can correctly identify and edit this example and one more, the problem is most likely to be one of monitoring for the error, not of misunderstanding the grammatical and conventional uses of written English. Ask the student how he ordinarily proofreads and suggest that he make a separate proofreading pass looking for this type of error.
Even if the student can correctly identify the first sub-category of error, don't assume that all the sub-categories will be equally obvious to the student. Go through at least one example for every sub-category of the kind of error before you move on to the next kind of error.