How do I write a good introduction for an exam essay?

Simply put, the introduction to your essay should provide a brief and assertive summary of your argument. You want to provide signposts for your reader, give the examiner a sense of where they are and where the essay is going. Also make sure to address specific issues in the question you have chosen to answer. You don't want to leave the marker in any doubt that you have understood, and are responding to, the terms of the question.

Don't worry too much about substantiation or illustration. The introduction should not become a 'mini essay' in and of itself. Discussion of historical detail and justifying the bold claims your introduction ought to make should be saved for the middle paragraphs. Likewise, don't get hung up on how to round off the introduction. Your conclusion is the appropriate place to summarise. The goal of the introduction is simply to guide the reader through your argument.