Otherwise, you may find that they have later abandoned you. Before writing your essay, outline your answer. Many students believe this process to be a waste of valuable test time. The opposite, in fact, is true. Knowing where you are going and being able to present the evidence in a compact, clear, complete, and logical fashion will almost always earn you a higher grade then throwing everything you know, without regard to relevance or direction, into an answer.
All good essays have three parts.
Most students spend too much time on the body of their answer and neglect, in some cases completely, the introduction and conclusion. And the conclusion, or summary, will reassert that point. Well, you shouldn't. Take the time to reread your essay. Look for misspelled words, words omitted, etc.