The first step with an essay is to collate the sources and resources needed to write the essay. Whether for you this means literary texts, scientific papers, critical essays, or whatever it may be, make sure you have the necessary material to respond to the essay stimulus. If you haven't already done so, you should familiarise yourself with the material by making notes on it, ensuring you understand the concepts to be discussed in the essay and knowing what information lies where. This is essential to the next step of the essay-writing procedure.
Good structure is absolutely critical to a good essay. Having a clear framework will make it easy for the marker to follow your thought processes, not to mention that this aspect almost always falls under the marking criteria. Basic structure begins with an introduction, followed by main body paragraphs, and ending with a conclusion, but each paragraph will have a different internal structure depending on your programme of study. But generally in an essay, the key features for each section include a thesis statement in the introduction, self-containment in main body paragraphs (i.e. each paragraph should begin with a topic sentence and end with a concluding sentence), and a summary of how you argued for your thesis statement in the conclusion.
Style of writing
An essay is a formal piece of academic writing, and this should be reflected in its written style. There are some things which should be avoided, such as colloquialisms (informal/casual speech), contractions (e.g. don't; can't; haven't), and the passive voice (i.e. when the subject is acted on by the verb, as in 'The lawn will be mowed by me'). As a rule of thumb, stick to the active voice as much as possible (i.e. when the subject performs the verb, as in 'I will mow the lawn'). You should avoid repetition of phrases and excessive repetition of individual words, employing a range of language as much as possible. When making comparisons, use comparators such as 'conversely' and 'on the other hand' to signpost to the marker that you are doing so. This might seem insignificant but, in reality, really helps to show the reader the point you are making.
Critical thinking is considered a higher-order skill and is often required to reach the top bracket of the mark scheme. Sometimes called evaluation, it demands that pupils consider the strengths and weaknesses of information and arguments. A good example is when writing a science essay, you should ask yourself of the experiments whether they used appropriate methods, a large sample size, and if the conclusions follow logically from the data. Alternatively, in philosophy essays, you should ask yourself of arguments whether they make weak or false assumptions, since these form the bases of arguments' conclusions. Evaluating the merit and validity of the information you are using is a key skill which when done well yields high marks in essays.
Similarly to what to look for when thinking critically, you should apply the same rigorous standards to your own work. This means making sure your assumptions are well founded, your conclusions follow logically from your premises, and you evidence your points satisfactorily (and explain why what you have provided constitutes evidence). As mentioned, the majority of essays need an overarching argument outlined in your thesis statement, and so the content of your essay should detail support for that thesis. If you are unsure of certain supporting information, it will rarely harm your mark to say so and why that may be; in fact, in most cases this will be rewarded under critical thinking. Essays are designed to convince the reader of a particular point of view, so try to put up a strong argument!
At university level and above, referencing is a necessary albeit unexciting part of the essay-writing procedure. It is, however, critically important and will be penalised if incomplete or done incorrectly. Different disciplines follow different referencing systems, so be sure to know which to use for your essay. If you are not sure whether to reference something or not, it is generally safer to do so since you avoid risking plagiarism or penalisation.