Remember that the introduction denotes the first paragraph of your essay that should be a short paragraph in which you should develop the points related to the subject of your essay. It should make the reader interested in having a further look at your piece of writing.
Depending on the topic of your essay, you may need to do some background research. This could be to find evidence to support your point of view or argument or to find out what people who are experts in the field thing about a particular subject. Or it could be to find scientific or historical facts or statistical data.