Before hanging your essay in do not forget to edit your piece of writing, look through it over and over again. Pay attention to the correct word order, grammar used in the sentences, proper spelling of the separate words and word combinations. Check the punctuation: commas, full stops, question marks etc. Verify if you have made all the necessary paragraphs of your essay. Avoid repetition, try to use synonyms to denote the same words, expressions, phrases etc. It is better if you scan your ready-made essay two or three times before having a final go.
Before you begin, make sure you know the word limit for your essay. You will usually be given a definite number eg 1500 words or 2000- 2500 words. If you are given a fixed number, it is usually acceptable to write 10% fewer or 10% more words. If you are given a range, try to stay within that range. However, check this with your tutor as you do not want to be penalized.