In a short essay, you have space for only a one-paragraph introduction. Once your essay gets beyond about 10 paragraphs, you can consider a two-paragraph introduction. In Tocqueville's book, the introduction is an entire chapter, but it does the same things that a one-paragraph introduction does: the introduction to an academic essay (1) introduces the topic, (2) sets up the argument of the thesis, and (3) points forward to the rest of the essay. In fact, accomplishing these goals begins as early as the title of the essay. Consider the title a significant part of your introduction.
Note that as you write, your idea of the topic, the argument, and the essay structure are likely to evolve. It is not a bad idea to write a quick setup of the problem and your solution as you understand it so far, write the rest of the essay, and then return to the introduction as the last section you carefully write.
Just to get started, you need a topic. See "What Makes a Good Essay?" for advice on choosing your goals, on key actions you can choose to perform in your essay, and on the kinds of paths on which you can lead your readers. If you are getting stuck, strike up a conversation with someone about the material you are considering writing about, or at least the general subject area. Often a topic will come out of that conversation. This is because under the pressure of coming up with things to say in a normal conversation, you will naturally move toward the more interesting, provocative, instructive, delightful, or moving topics.
Take this possible conversation starter as an example: "I loved how everybody at that performance of The Taming of the Shrew wore modern clothes. It really made me feel that the story could have happened in my old neighborhood. Then, when Petruchio came to his wedding as a biker, I could really see how he was trying to make a point. He wanted to show everybody that he could wear anything he wanted--that he was in control. That got me thinking how we always like to make every detail perfect at a wedding, but it's so easy for one thing to break up the whole experience."
Once you have narrated some ideas and put them down on paper, turn the conversational style into a more formal academic style. Note that you often will have to specify vague terms that you used earlier. This version will be enough to launch the paper until you are ready to revise. Let's use Tocqueville's model:
"Among the many flashy costumes that update the lifestyles of the characters in The Taming of the Shrew for contemporary audiences at the Shakespeare Theater, no costume is more striking than the biker garb that Petruchio wears to his own wedding. It might be hard to appreciate Renaissance formalwear, but everyone can understand the white dress worn by Katherine on her wedding day. When Petruchio matches her beautiful dress with black leather instead of a tuxedo, he draws the surprise of everyone. Petruchio uses this attention to show everyone that he is controlling the fate of Katherine. Not only that, he shows everyone that enjoyment of the wedding depends on him. In fact the biker garb of Petruchio does more than strike fear into the wedding party; his upending of formalwear, of weddings, of the solemnity of a religious service, challenges us to acknowledge the fragility of our most carefully scripted experiences."
By the end of the introduction, your reader should be able to understand what you are doing and why you are doing it. In other words, what is at stake? Why should the reader read the essay? In the example above, readers might be interested to join you in working through the challenge presented in the last sentence, if they trust that you have thought enough about the challenge to lead them through it.