Start Early. If you wait until the night before an essay is due to begin it you are doing yourself a great disservice. You simply will not have enough time to learn and understand the material, let alone write a decent paper. You need time to absorb the information, reflect on it, and form a solid position and argument. One of the worst feelings is trying to write a paper last minute and at 2 am realizing you have suddenly have a strong opinion and feelings about this assignment but are far too exhausted and short on time to do the proper research and write something good. Besides, anything you write the night before it's due will be a rough draft and will likely be riddled with spelling errors and grammatical errors.
Pick a topic that interests you. If you already feel passionate about the project you are more likely to start early and put in an effort that reflects your passion. Teachers can feel whether or not a student cared about what they were writing about when they grade the assignment. Admiration for your passion will translate into at least a couple percent on the grade you receive for your essay. So you need to brush up your writing skills to create a great essay in school.
Research
Read the material you are writing about, then Google it. Follow up on as many links and resources as you can both online and in a real library with real books. The more you read the more you will understand what you are reading about. The material has a way of beginning to “gel” together in your mind. Only when all the resource leads you follow lead to resources you have already read then you will know you have read everything there is to read on your topic. Only then are you qualified to have an opinion and begin writing your essay.
Mimic your teacher
This doesn't mean side with his opinion when you write essays. If you write well and convincingly a fair teacher will give you a good grade regardless with whether or not you side with him. What it means is pay attention to your teacher's language, words, phrases, tone; even body language, gestures, and overall temperament towards a subject. If you can effectively mimic your teacher the subtle flattery makes it easy for them to read your essay. It makes it easy for them to like your essay. It makes it easier for your teacher to read, like, and give your essay a good grade when they don't have to try too hard to wrap their mind around what you are trying to say.
Revise and edit. If your teacher offers to criticize your rough draft before the due date takes full advantage of this! If the person who will be grading your essay offers to tell you exactly what is good and what is bad about your essay, and allow you to revise it, it is the same as knowing the questions and answers to a test before the test! It is foolish to ignore this opportunity. If your teacher doesn't, find out if your school offers an essay editing program, or if there are older students who tutor and proofread. Parents can be helpful too.
Proofread and edit
Slightly different that revision which revises ideas, proofreading eliminates errors. With online dictionaries and proofreading software for free there is absolutely NO EXCUSE for spelling errors and grammatical errors. An essay might have good ideas and a sound argument but the teacher might knock off 10-20% simply because you have too many of misspelled words and comma splices.
Avoid plagiarism
It is your responsibility to make sure that you are not copying the phrases or ideas of someone else. It is possible that you came up with an idea all on your own that others already share but it is your responsibility to prove how your research led you to forming that idea yourself. Make sure to source any quotations or information you share in your essay that are not your own. Depending on the level of your Academia simply sourcing is not good enough; you need to source properly according to the style you are writing in. It is also considered plagiarizing if you copy yourself. If you've already handed in this essay, or many chunks of it to any other teacher or class, you can't use it again unless you properly source yourself.