Gather research for your topic from a variety of different and current sources. Using sources that are as current as possible allows the inclusion of newer information regarding Rockwell and his work which may have only recently come to light. Avoid taking the bulk of your information from multiple references written by one author, for diversity of opinion and interpretation regarding Rockwell's art. Ask your instructor or editor how many references they require you to work with.
Begin constructing an outline of your essay before you begin the actual writing. Let the length of your essay define the scope of your topic. For example, a short essay might be best served by focusing on one particular Rockwell painting, while a longer essay could examine Rockwell's political views on his entire body of work.
Write down all of the main ideas you wish to include in your essay, and list other related sub-topics underneath each main idea.
Write the first draft introduction of your essay. As the beginning of your essay, the introduction should provide a general statement about your topic and give a clear indication as to what you'll be specifically focusing on investigating, arguing or elucidating. If this essay is for publication rather than academic work, it's especially important to make the introduction as interesting as possible so as not to lose the reader.
Begin writing the first draft body of your essay. Include the bulk of your research information here, if not all of it, and organize your body paragraphs so that each one deals with it's one idea subset of the main topic. Think of each paragraph as a mini-essay. Transition between paragraphs smoothly with well-written segues, so that the reader is guided along your thought process. Back up each point made in every paragraph with quotations from your research.
Begin writing the first draft conclusion of your essay. Give a summary of the main points in your essay. Leave out the details and researched quotations that you've already included in the body. Use the conclusion to also restate the main idea of your essay.
Revise the draft, refining any unclear arguments, backing up unsubstantiated claims with research quotations, re-organizing paragraphs in the body of the essay, and rewriting poorly constructed sentences. Read your paper out loud to hear mistakes you may not have noticed through silent proofreading. Have a friend or family member proofread your essay to see if your writing is clear and persuasive to others.