A dissertation introduction is meant to lead into the main body of the dissertation. Overall, you want to leave a good impression on the faculty reading your dissertation by putting your best foot forward in the introduction. This is best done by using a sample dissertation as a template to work from.
Before you start, you can brainstorm all ideas, facts, and expressions you want to use. Once you’ve done that, write them down. Remember who you're writing for and avoid trivial information, overly generalized statements and well-known, redundant facts. The introduction should be simple, but not simplified. Use the sample you’ve bought to see how these tips play a part in the writing. Fashion your writing in the same way by continually referring to the template you have.
If you can't start on your own and don't want to deviate from the norm too much, here is an example of a strong structure that always produces acceptable dissertation introductions:
If you have a decent sample, you will see these features pop up too. Measure your own work against these guidelines so that your dissertation contains all the necessary style points it needs to get acknowledged.
There are, however, several problems with using a sample to write your paper. Although it generally produces ready-made dissertations, it leaves the impression of mechanicalness and the quality of it cannot rise above 'acceptable' without your creativity. It's up to you to find a way to make the introduction sound lively and interesting. Remember that your teacher probably read this exact same thing a thousand times. Make your introduction pop out, while still keeping the academic tone throughout. Keep your introduction short, relative to the length of the entire dissertation.
If you've brainstormed ideas before you started writing, use them sparingly in the introduction and save the majority for later. Plan ahead and distribute your best material (spoilers) to keep the attention of the reader throughout the text.
Keep in mind that each chapter you write should be self-contained and not require too much context outside logical explanation to understand what it is about. Try to structure your material in such a way that each paragraph only references what is in following paragraphs immediately before and after it. The reason for this is that the reader's attention may tend to drift away if you don't place reminders ever so often. The reader may also get lost if you don't connect a chapter with the preceding and following one.