Essay exams are not opportunities to express personal opinions about topics. An essay exam is where you can logically express what you have learned from the readings, lecture and other presentations in the class. The essay question is a way to organize the information you have and to express it in a logical way. It is a means for you to demonstrate your understanding and mastery of the material presented in the course. It is not an occasion to argue with the professor or the author of the text. When grading an essay I look for several things: 1) information provided to answer the question; 2) logic of the presentation, 3) examples provided to illustrate your main points, 4) clear understanding of concepts, theories and academic arguments made by authors, etc.
Although points for spelling and grammar may not be deducted, they count in the overall presentation. Poor spelling and grammar detracts the reader from the ideas you are trying to express and leads the reader to think you are not good at communicating your ideas to others. Don't rely on your spell checker, proof read! Poor spelling stops the progress of the reader as they try to figure out your meaning. Poor grammar indicates that you do not know how to express your ideas. Both interfere with communication and separate you from your reader. Under the pressure of an exam, you may make mistakes but if you have good spelling and grammar to begin with this is less likely.
It is often beneficial to prepare for essay exams by outlining the material covered. Where study questions are provided they are a good place to begin. First identify the logic of the question: compare and contrast, critique (this implies the application of a criterion to a specific event or presentation of ideas, you must know what criterion you are to use and identify it in your essay), illustrate, strengths and weaknesses, pro and con, factors that affect. These are all different ways of providing discussion of issues (which have more than one side) and topics. These also set the pattern for the essay. Outline your topic in light of the logic of the question. Then go to your notes and find the relevant information for the sections of the essay. It is easier to memorize an outline than a written paragraph. Prepare an outline that covers the main ideas you want to include with examples. Where relevant provide definitions of concepts that have been taught so you can show you understand them. After you have prepared your outline, try to write an essay without looking at your outline. This will tell you how much of the material you have remembered. If you have not been provided with study questions, create your own. From the way the material has been presented you can logically deduce questions you might be asked about the material. Then prepare an answer as discussed above.
In an essay exam it is up to the student to demonstrate how well he or she knows the material. No guesses here. This preparation is time consuming. It requires effort. It will produce good grades if you conscientiously do it.