What is the best way to approach writing an introduction to an essay?

The most important thing about an introduction is instilling a confidence in the reader or marker that you know what you are writing about, rather than making it up as you go along. Therefore it is often a good idea to simply state your answer to the question posed to you, followed up with how you plan on proving your point of view in the rest of the essay. So for example if the question were 'To what extent does the author present character x as the antagonist in the novel', one's introuction may take this sort of structure: 'Upon analysing the text, it would seem that the author in fact presents character x as the protagonist, rather than the antagonist. There are a number of ways in which he achieves this that I shall analyse during the course of ths essay. They include, firstly, the contrast between character x and the true antagonist character y in the last chapter; secondly, the feeling of pathos created for character x when her friends start to abandon her... etcetera' Not only does this display confidence to marker or reader, but it also helps you to structure your own work as the introduction acts as a plan for the rest of the essay.