Before giving an expanded answer, you consider the preferences and likings of a person who asked it. You should think about the same when writing your essay. Before getting started, you should consider the following factors that may influence your writing process:
If you focus on attempt to impress a university professor with your work there is a lot to consider. Your language should be casual and no colloquialisms used. Think over your style carefully. Formal approach would be the most proper in such an essay, but you can make it sound more subjective. Impersonal attitude given in the essay is most likely to show the blank procession of the literature and other possible sources. The requirements are to state personal opinion, not to make up a summary of what you've read; therefore semi-formal style would be a nice decision for any essay. Don't be conservative and state your opinion, but be careful with an attitude you express towards the subject. Some of them are good for discussion after classes but not in your essay that influences your grade.
Sometimes students attempt to fill their papers with flamboyant emotional outbursts that make the essay richer. Usually it works, but frequently some types of essays are not to have strong confirmation sentences and utterances exaggerating facts. For instance criticism requires objectivity and plain evidence with no overestimation. In general, rich vocabulary will only be appreciated. A little remark to the previous statement: do not drown the core in fancy phrases; state it plainly, but make an explanation sound beautifully.
And finally, take into account preferences and ideas of the audience. If you venture to affirm an idea that is contradictory to an opinion of the professor, the result may turn out quite unpredictable. When writing a paper, common sense and logics are good advisers.