Your introduction should tell the reader what to expect from your piece of writing.
What should be in an introduction?
There isn't one way to write an introduction. Your introduction should tell the reader what to expect from your assignment. It should present the main subject of the work so that your reader is clear what the writing will be about.
You should also explain why your topic is important and worthy of discussion. You may wish to highlight relevant publications to show how your argument fits into a wider context or conversation.
You might also provide definitions for any ambiguous terms or concepts; your reader needs to know what you mean or how you have interpreted them. For example, if you use "consumerism", are you discussing this as an ideology, economic policy or type of behaviour?
Your introduction should also give an indication of the structure of the rest of the assignment.
How long should an introduction be?
An introduction usually makes up 5–10% of your assignment, although there is no absolute rule.
The amount of detail that you can include in your introduction will depend on your word count.
Examples of introductions
Take a look at this detailed example of an introduction (PDF), which is broken down to show the purpose of each sentence within the introductory paragraph.
There is also an example of an introductory paragraph in the Examples of paragraphs in academic writing resource.