Review your essay carefully, very slowly, sentence by sentence for subject/verb agreement, tense sequence, plurals and possessives, sentence fragments and run-on sentences. Once you have checked all of these things, check again; they are very easy to miss.
The following are some particularly important questions to consider with respect to grammar in your essay:
- Does each subject agree with its verb (e.g., “the girl works”; “the girls work”)?
- Is the tense of your verbs appropriate and consistent within each paragraph?
- Can each pronoun (he, she, they, it, etc.) be easily traced back to the person or thing to which it refers?
- Are all your sentences complete and appropriate in length?
- Does each sentence have a subject and a verb?
- If sentences are combined, have you used a conjunction or a semi-colon between them?