How do I write an introduction to an essay?

The introduction to an essay is essentially the section where you can highlight the key points of your argument; it is useful both to the author and the reader as it helps to give the rest of the essay a sense of structure and cohesion. For example, were I to write the introduction to an essay discussing the portrayal of race in Shakespeare's Othello, the key points I would introduce would include: the author's name and the time of publication (for context); perhaps the era's perception of race, in this case early 17th century England was a highly prejudiced and white-dominated place to live in; I would touch on some of the other characters' perception of race and bring in one or two quotes, to give the reader a 'teaser', so to speak, of what is to come, and finally, I might mention how race interacts with other key themes in the play, for example class, gender, and inequality. This is only one example of how the introduction could play out, but hopefully it highlights some of the integral foundations of any good introduction. It should establish a clear argument for both yourself and the reader to follow; it should give context, and it should begin to bring in some of the more analytical writing which the reader will find in any following closely analytical paragraphs.