Write an essay outline before you begin. The outline will help you decide where you are going and where you want to end up. You can use any outline format you want, just make sure your outline contains all of the parts of what you want to write.
To pass, your essay needs to have a main focus. You cannot ramble or go off on tangents. Your main focus might be in your essay assignment, or it might be the main idea you are getting to when you write your essay. Keep your focus in mind the entire time you are writing, and do not stray from it.
To be a good essay, yours should tie everything together between the beginning and the end. If you begin with a personal story or anecdote, make sure you return to it in the end. If you talk about a particular idea when you start, come back to that essay. Bookending your essay with similar ideas makes your essay flow better. If your essay has a beginning, middle, and end, you are on the right track.
The easiest way to flunk your essay is to use incorrect grammar or punctuation. Depending on what the essay is for and what level you write at, those reading will want to see that you know how to write well. Write in active voice whenever possible and avoid passive voice. Make sure the tenses of your verbs and subjects match each other. Use correct punctuation, especially apostrophes, which can change meaning - such as "your" compared to "you're." Use the spell check on your computer, or have someone edit your paper for you to make sure you have spelled everything correctly. Double check the essay's requirements to be sure you have left correct margin sizes, that your pages are numbered according to the requirements, and that your essay is the correct length. Avoid slang and inappropriate words. Write in full sentences and use paragraphs to separate information.