Here are some suggestions on writing the introduction to your paper.
It’s a contract between the author and reader. Make sure that the introduction corresponds to what the paper actually says, and vice-versa. If you say in the intro that you’ll cover something, then be sure to cover it.
Write a rough version of it early. Free-write your introduction early on. You’ll revise it significantly, but I’ve always found that forcing myself to write the introduction early on gets me thinking more holistically about how the parts of the paper fit together.
Come back to the introduction as you revise. Don’t spend to much time on your introduction, but it helps from time to time to do a “reality check” by looking back at your introduction. Are you forgetting things that should be in the paper? Has your thinking changed? Do you need to reorganize what you say, and where?
Revise it carefully at the end. As noted, the final version of your introduction should match what you actually say in the body of the paper.
Length. For a 30-page student paper, I’d recommend that your introduction be no more than 2-4 pages. If you believe it needs to be longer, chances are you are trying to put background information in the introduction that should instead go elsewhere.
Components of an introduction. See Fajans and Falk pp. 87-88. A good introduction should include matters discussed there (and credit to Professor Eugene Volokh for his discussion in Academic Legal Writing regarding utility/novelty/nonobviousness):
Your topic. What is the problem or question your paper addresses?
Your thesis. What is your answer to the question, or your solution?
Utility. Don’t actually use the term “utility,” but be sure to explain why your topic and thesis are important to the reader.
Novelty & nonobviousness. Don’t use those terms, but be sure to explain why your paper contains something new, and why your original contribution is more than an obvious addition to what came before.
Roadmap. The introduction traditionally closes with a roadmap that lists — by part — what each part of the paper will do. For example, here’s a roadmap from my article Civil Procedures for a World of Shared and User-Generated Content, 48 U. Louisville L. Rev. 911 (2010) (part I is not listed below because it was the introduction).
“Part II notes how the interplay between copyright substance and procedure can lead to a substance-procedure-substance feedback loop. It also lays out a descriptive framework for copyright procedure derived from the actors, sources, and functions of those procedures. Part III examines three major types of private enforcement procedures, namely direct, indirect, and automated copyright enforcement, and considers how they foster feedback loops. It also makes a number of suggestions aimed at improving the balance between owners and users. Part IV considers the values attendant to procedural justice in copyright enforcement, and sets forth a normative framework that looks to principles of participation, transparency, and “balanced accuracy” that might lead to private enforcement procedures that better accommodate the reasonable cost and efficiency needs of copyright owners without trampling on UGC.”
Last revised Oct. 7, 2014