Introductions and conclusions can be the most difficult parts of papers to write. Usually when you sit down to respond to an assignment, you have at least some sense of what you want to say in the body of your paper. You might have chosen a few examples you want to use or have an idea that will help you answer the main question of your assignment: these sections, therefore, are not as hard to write. But these middle parts of the paper can't just come out of thin air; they need to be introduced and concluded in a way that makes sense to your reader.
Your introduction and conclusion act as bridges that transport your readers from their own lives into the "place" of your analysis. By providing an introduction that helps your readers make a transition between their own world and the issues you will be writing about, you give your readers the tools they need to get into your topic and care about what you are saying. Similarly, once you've hooked your reader with the introduction and offered evidence to prove your thesis, your conclusion can provide a bridge to help your readers make the transition back to their daily lives.
You never get a second chance to make a first impression. The opening paragraph of your paper will provide your readers with their initial impressions of your argument, your writing style, and the overall quality of your work. A vague, disorganized, error-filled, off-the-wall, or boring introduction will probably create a negative impression. On the other hand, a concise, engaging, and well-written introduction will start your readers off thinking highly of you, your analytical skills, your writing, and your paper. This impression is especially important when the audience you are trying to reach (your instructor) will be grading your work.
Your introduction is an important road map for the rest of your paper. Your introduction conveys a lot of information to your readers. You can let them know what your topic is, why it is important, and how you plan to proceed with your discussion. In most academic disciplines, your introduction should contain a thesis that will assert your main argument. It should also, ideally, give the reader a sense of the kinds of information you will use to make that argument and the general organization of the paragraphs and pages that will follow. After reading your introduction, your readers should not have any major surprises in store when they read the main body of your paper.
Ideally, your introduction will make your readers want to read your paper. The introduction should capture your readers' interest, making them want to read the rest of your paper. Opening with a compelling story, a fascinating quotation, an interesting question, or a stirring example can get your readers to see why this topic matters and serve as an invitation for them to join you for an interesting intellectual conversation.