How do I write a good introduction?

The introduction is the crux of the essay in which you clearly set out your line of argument. I would start my introduction off with a quick summary of the historiographical debate surrounding the question, if there is any, before then introducing my own thesis. This lets me to situate my answer within the relevant historiography, allowing me to clearly engage with the debate at hand. After presenting my argument, I can develop the themes through which I am going to argue my thesis, stating why they may be relevant. This should not be done in significant detail, however, since this will manifest itself within the main body of the essay. Importantly, if there any terms that need to be grappled with, be it via definition or questioning, the introduction is the place to explore them and present your own take on them. Examiners generally prefer it when students engage with the question by exploring the scholarly debate and tackling any underlying assumptions that may be present within the question itself.