Why not begin by looking at the academic writing guide and its links for more support.
The first draft
Few people can write the final version of their assignment straightaway. It is likely that you will need to make some amendments to your first version to make sure your arguments are stated clearly and that you have answered the question. You will also need to keep an eye on your word limit and add or delete content if necessary.
When putting together your draft there are a few key things to consider:
Structuring your work
Always check with your tutor about his/her requirements.
See the guide to structure
An essay will typically include:
Introduction (5-20% of essay length)
Body (60-80% of essay length)
Conclusion (5-20% of essay length)
What you say in your conclusion should match what you said in the introduction: it should re-state (but not repeat) your idea or argument, ideally showing more fully what you have been saying. Remember the conclusion is the last thing the reader looks at, so it needs to leave a good impression!