I expanded on and revised the advice below: original document available at the Web page “Guidelines for Writing an Essay,” by Dr. Margaret E. Mitchell at the University of West Georgia:

CRITICAL THINKING: by integrating critical thinking into an essay and by reflecting on your intentions, you will want to ask a key question early on (for readers will do so in their own mind). The Key question: “So what?” Meaning: what is the significance of what I am about to write? We explain to readers WHY our investigation of an open-ended, research question matters. We show readers that we are trying to figure something out. This “something” serves as a purpose for writing. If you keep a purpose for writing in mind while constructing your essay, chances are, in the end your essay will be more cohesive.

In advancing an argument, objectivity plays a role: reporting facts obtained through competent research fulfills the expectation that writers provide evidence for their perspectives. But more so, writers have to show readers their perspective and reflections on those “facts” as they go along, directly linking reflections to the exploration and expression of a controlling idea or research question. In other words writers interpret and infer how the data matters and how the observations can be applied to the “So what?” question.

Let me put it another way: “The Big Picture.” I ask myself not only if the writer gives readers an important, significant, and challenging point he or she is trying to make, but also whether of not readers can identify the writer’s purpose? Is this purpose central to an entire essay? A controlling idea requires that writers develop their own purpose for writing, beyond any factual observation of what an artist or author or philosophor accomplishes. Why does it matter? Think about your audience: What is at stake? This kind of inquiry and reflection can help establish YOUR purpose for writing, separate from the related purpose of the text you are reading.

Structure, Organization, and Logic:

Dr. Mitchell writes, “ I also look at the logic connecting a writer’s ideas together, and I examine the framework used to structure those ideas.  A strong critical essay has a clear sense of development, progress, and forward motion: it doesn’t keep repeating the same ideas, and it doesn’t move in circles or travel through unrelated information on a list."