A good introduction is key to a good paper. A good introduction gets the reader's attention and lets them know what to expect in the rest of the paper. A bad introduction tells the reader to stop right now, because it's not getting any better from here. We'll show you how to write a good one below.
Know what you are introducing. Many novice writers think that they must write the paper in order, starting with the introduction and going on from there. While that may work for some writers, it is important to know what the rest of your paper is going to say before you try to come up with a good way to introduce it.
Grab the reader's attention. Try to envision your target reader as someone who does not have to read your paper. You need to grab their attention in the beginning and tell them that they should keep reading. The first few sentences of your paper should do this. Some good strategies for grabbing a reader's attention at the beginning of your paper include a compelling anecdote, a clever quotation, or a startling statistic.
Get to the point. An introduction is not a time for flowery language. Address what needs to be said in an introduction.
Tie your attention grabber to your thesis. After you have grabbed your reader's attention with your first few sentences, you now have to show how this relates to the thesis of your paper. Transition from your attention grabber to your thesis. The length of the transition will vary, but try to keep it as short as possible, as you want to quickly get to your thesis and then to the body of your paper.
Conclude your introduction by stating your thesis. Many instructors explicitly require you to put a thesis statement at the end of your introduction. Others do not. Regardless, it is a good idea to end your intro by telling your reader what the rest of the paper is going to be about. This may or may not be a traditional "thesis statement", and it may take more than one sentence, but it should make it clear to the reader what the paper is about.