How do I write a good introduction to an essay?

The introduction to your English essay is all about opening up, clearing up and getting your readers prepared for the nature of your answer. In other words, the introduction should warm your reader up to the points you intend to make. The introduction is intended to prevent confusion when your reader begins the essay. It should provide clarity and a pre-emptive structure, to keep your reader from getting lost along the way.

It is common for the introduction to be described as a 'summary' of the essay as a whole. Unfortunately, this notion can lead to some confusion about what an introduction should entail. It detracts from the idea that the introduction should, in fact, be a gentle way of preparing your reader for the intensive content ahead of them. After all, if a reader enters the essay without the faintest idea of where it might be going, it may take them several paragraphs to understand the essay's argument. By which point, the previous paragraphs have been rendered useless. It is important to outline the argument of your essay in the introduction, like mapping the route of a journey. 

Without the introduction, readers often find themselves lost and bogged down in what can seem like an erratic essay structure. 

So, instead of thinking of the introduction as a 'summary', begin thinking of it as an opportunity to give your readers a glimpse at a map before they embark on a journey. At the very least, this will help them understand the route.