The standard way to think about structuring an essay is in three parts.
Introduction
This should explain why the question is important. It should also signpost how you are going to tackle the question in the main body of the essay and it can include the conclusion of your argument.
The introduction should be short and concise – you rarely get any marks for it directly. Most students spend too long on their introductions, at the expense of their analysis and conclusion (especially in exam questions).
Main body
This should be a series of paragraphs. Each might be a self-contained argument (which follows the Thesis – Justification – Support rhetoric) or the argument might be spread over several paragraphs (if your justification is long, for example).
It is important to make sure your paragraphs flow logically. Typically they will be ordered in terms of importance, although other orderings are possible (e.g. chronological).
Conclusion
This should restate your main argument (although not in exactly the same words as the introduction). You can remind readers why the issue is important, and make some tentative policy implications from your analysis.
It might also be possible to mention other considerations which are possible areas of future investigation but which you haven’t had time/space to address.
See Bray et al. for more about structure.