Consider the topic you want to communicate or share with the audience. The topic itself will help to determine the purpose of the essay. Essays may be divided into four groups or categories: narrative -- narrate a particular series of events or occurrences; descriptive -- focusing particular people or places; expository -- elaborating on certain ideas and concepts; and persuasive -- attempting to convince the reader about a certain point of of view or course of action.
Consider the intended audience. A well-written essay should be crafted to the needs of the particular audience or readers. Writing an essay for an academic audience means using different language and images than you would in an essay written for a union organizing meeting. For example, if you are writing an expository essay, use language that resonates with the feelings, moods and expectations of the audience. One of the reasons Martin Luther King Jr.'s speeches resonated so powerfully with the Civil Rights movement was that he utilized the vernacular and imagery common to the African-American church experience. On the other hand, if you are writing a persuasive essay, the audience may not be as sympathetic or may even be hostile to the message. Choose words and images that will provoke a strong emotional impact that helps to bring the reader around to your point of view.
Consider the time frame for the essay. Some essays are written for the moment. They address and comment on particular historical events that are relevant at the time to a particular audience. Other essays are more universal in nature and their message is intended to have a more timeless appeal. The great American essayist Ralph Waldo Emerson represented the best of both worlds. His essays were written to address particular themes of the American experience in the first part of the 19th century, but the ideas, themes and topics in his essays still resonate with readers today.