The way you lay out your introductory paragraph largely depends on what your task is. For example, if you have thirty minutes to write a comparative essay, your introduction is going to much briefer and in a style altogether different, than in an Extended Essay on poetry.
However, every introduction should answer these basic questions;
1. What am I writing about?
(If you have been given a text to analyse, you should explicitly name the author and title)
2. Why is this important?
(This should be a very brief mention of why the topic is an important/ influential/ intellectually engaging one)
3. How am I going to approach the question/task?
(If you know that your word count or time limit inhibits you from exploring the entire topic thoroughly, then you should set a scope. For example "A Midsummer Night's Dream will be used to analyse how Shakespeare used this particular style, as this text is a most significant example of"...)
4. What is my thesis statement, and what am I going to conclude?
(This is one of the most challenging parts of the essay, but if you get it right, it'll help facilitate the rest of your writing, as well as lay out your arguments in a clear and concise manner. It seems counterintuitive to think about the conclusion whilst you're writing an introduction, but it's crucial to give your essay a sense of direction. If you evaluate what you want to conclude, then you can set out the relevant arguments from the beginning, this will make your essay persuasive and help you avoid self-contradictions.
Your thesis statement is just what is says it is – spelling out what you believe is the right answer or method of approaching the problem. For the purpose of clarity, your thesis statement should also dictate the structure of your essay's body. For example, if your thesis statement says "TopicA, will be analysed in terms of aspect1, aspect2, and aspect3", then in your body, paragraph 1 should consider aspect1, paragraph 2 should consider aspect 2, and so on.)
General Tips; Always try to imagine that a random person, who hasn't read the task/question, has picked up your essay. Can they get a sense of what it's about from the introduction?