If you are writing a research paper, a book or even a short story, a preface helps to introduce your subject matter to a reader. It should be brief, and it comes before anything else you've written. The purpose of a preface is to persuade your reader why she should read the rest of your written work. Writing a good preface will incorporate your personal reasons for exploring your written subject while, at the same time, persuading your reader to continue reading.
Explain why you’re interested in this topic. Give a personal anecdote; for example, explain that you had a teacher who interested you in this topic, or write about how, for instance, you went to Spain and it was there that you decided that you wanted to study Modern Spanish architecture. Make this a paragraph or two long only.
Explain why the topic is important to you and why it should be important to the reader. It’s not convincing, for example, if your only explanation about why people should read your essay about roses is because you think flowers are pretty. Make sure to include what makes your writing or your subject unique, especially if many essays have already been written about your chosen subject. A preface to a collection of love sonnets, for another example, might say that they are relevant because of how they rework conventional forms of language.
Give examples of who has written about similar topics to the one you have chosen. These examples are often called "secondary references." In case readers are interested in your topic, this will help them to know where to go to look up similar books, articles or essays. The number of paragraphs you will need to write for this step depends on how many secondary references you want to list. Depending on how much research you want to discuss, this section can be as short as one paragraph, but it can be much longer if your topic has a long history.
Thank people you know who helped you along the way. A preface often includes a list of friends and colleagues the writer would like to thank who helped her with research. Do this at the end of your preface in the last one or two paragraphs.