Essays should be able to answer questions if one is given or, if none is specified, it should address the implied issue, topic or subject. It should concentrate on these items. If you intend to divert or change the topic, you should give a justification for doing so. In writing your work, you should give a clear argument by starting with working from premises through evidence going towards your conclusion.
You may also need to present in essays both the sides of in favor or against the argument involved. Do all these with a clear and logical outline. Further, you must define the terms of the question in the clearest possible way that you can. This way, whatever conclusion you will arrive at can be compared or verified using the terms in which the problem was set in the writing assignment.
If essays refer to literary or other textual sources, you should write an answer that concentrates primarily on the relevant text or texts. You should use them as the main source of argument and illustration. You can also make reference to a broader context like biographical and historical ones. Usually, it is this wider context which is required of you. On these instances, you should firmly keep the focus on the question.
To guide yourself when writing, you can keep in mind a certain kind of reader. It is better that this person you paint in your mind is one who has the intelligent interest in the subject and, at the same time, have no or little specialized knowledge on the topic. Use quotations to help you support your argument. This also means that you should not use them when they do not. If they do not specifically do so, they should illustrate a point which is worthwhile or direct a focus on a detail which is important. Examples of these are phrases or sentences which have given rise to controversy and conflict in how ideas are construed. Set texts must be quoted in the language it was originally in.