Think of yourself as proposing possibilities, not dictating revisions. It is the writer, after all, who will have to grapple with the task of improving the essay. Work with the writer to identify the strengths and limitations of the draft.

Restate the writer's main ideas.

It's helpful for the writer to see if you understand the main point of the essay. Restate the thesis for the writer. And try to paraphrase each paragraph of the draft to help the writer see if the essay's points are clearly expressed.

Where possible, give specific compliments.

Vague compliments (such as “I liked your essay”) sound insincere—and they aren't helpful. Point out specific successes. For example, you might mention that you particularly admire how the writer presents the opposing viewpoint in the second paragraph before challenging it in the third.

Link suggestions for improvement to the writer's goals.

Criticism is constructive when it is offered in the right spirit. For example, you might advise the writer to put the most dramatic example last, where it will have the maximum impact on readers.

Ask questions and tell the writer where you would like to hear more.

Note passages that you found either confusing or interesting. By asking for clarification, you will help the writer see what needs to be revised. Indicating an interest in hearing more about a topic will often inspire the writer to come up with useful and vivid details.

Express interest in reading the next draft.

When your interest is sincere, expressing it can be a powerful motivation for a writer.