Your score on the essay section of the GRE exam is used by graduate schools to evaluate your writing and analytical skills. Two separate trained readers will read your essays. They will score each essay based on many factors, and the scores will be combined and averaged. Scores are given on a range from zero to six, in half-point increments. The ETS provides the criteria that are used to score the issue and argument essays. Although in the essay section grammar and spelling are important, it is much more important that you concentrate on writing a coherent, complete, and persuasive essay.
Whenever possible, use strong subjects and active constructions, rather than weak verbal nouns or abstractions and weak passive or linking verbs: instead of "Petruchio's denial of Kate of her basic necessities would seem cruel and harsh...," try "By denying Kate the basic necessities of life, Petruchio appears cruel and harsh--but he says that he is just putting on an act." Don't forget that words and even phrases can serve as strong sentence subjects: "Petruchio's 'I'll buckler thee against a million' injects an unexpectedly chivalric note, especially since it follows hard on the heels of his seemingly un-gentlemanly behavior." And remember--use regular quotation marks unless you're quoting material that contains a quotation itself.