The document outlines 5 common mistakes in writing commentary: 1) commentary that is too generic, 2) commentary that drifts from the topic sentence, 3) commentary that provides too much concrete detail, 4) commentary that repeats itself, and 5) commentary that contradicts the topic sentence. Examples of each mistake are given along with suggestions for improving the commentary. The goal is to avoid superficial or inconsistent commentary and instead provide analysis that ties back to and deepens the topic sentence.