Do what your teacher says! If the instructions call for a 500 word book report - write a 500 word book report. OK, 490 will do...but 400 won't. If the instructions call for a 1850 word research essay -1800 might let you scrape through, and you could even run a little long...1950 words maybe...but NOT 2500!!!! Stick near the required length - a little long or short won't hurt you (too much...),but the length is there for a reason; that is the scope of the essay the teacher is looking for. The word count gives you a real indication of how indepth, complex, or concise the essay must be. Look for hidden extras though - do you have to report on a certain amount of sources in that research essay? Does your book report have to include a summary or does it specifically ask you to exclude it? In an opinion essay - are you asked to also give an opposite opinion for contrast? Are you expected to quote from stories or books if you are writing about them? Read the instructions! Find out! If you're still not sure - ask the teacher.
Essay questions come in a wide variety. Sometimes essay questions are easy to recognize as questions, i.e.: Are books useful when we have greater and greater access to computers? But other questions don't look like questions at all, i.e.: ee cummings wrote challenging poems which once unlocked are full of meaning and emotion. That is clearly a statement - but at the same time it's a question - you have to accept or deny and then make your case and show it. Some teachers write assignments phrased as an essay title which you must use, then they explain the ideas and questions you must think about in order to write an essay that explores that title. Sometimes an essay question will have many parts, sometimes it will be a single word. Sometimes you'll have a choice, and sometimes you won't. Whatever type of question it is, don't fight it!!! If there is more than one to choose from - take the one you can grasp and twist around in your head. I repeat - once you have your question - don't fight it! The more you don't like it, downgrade it, argue with it, yell at it, think how pathetic it is, or say that you can't possibly write an essay about it - the harder it will become. So relax! Look at your question, mull it over, sit back and ponder it and see what unfolds. Don't expect the whole answer to materialize in your head - instead, fish around and see what's there. Write down what you find. Then go to Brainstorming/freewriting to help you spin out more. If you're sitting there and nothing whatsoever is happening go to the next paragraph - it might help...