Good essays are well planned. So make a plan on paper before you begin to write the essay. If you don't finish the essay, include your plan in what you turn in. You may get part marks.
Good essays have a thesis (a provable claim) that is supported by facts, argued through the use of good paragraphs. If you don't know what a good thesis is, you need to learn right away. If you don't what makes good evidence in an argument, you need to learn right away. Good essays are built on good paragraphs. If you don't know how to write good paragraphs, you need to learn right away. All the paragraphs in your essay should be connected to each other by transitional words and phrases. If you don't know what transitional words and phrases are, look them up and learn 10 before your exam. Good paragraphs are built upon good sentences. If you don’t know what a good sentence is you need to learn write away. Very your sentence length.