Begin your introduction with an attention-getter. Some examples include a statistic, an alarming fact, a question or a quote from the distinguished person. Avoid cliché phrases like, "Since the beginning of man," "According to the dictionary" or "There is something that's sweeping the nation." This first sentence should pique a reader's interest and make him think, "Wow. I need to read on." For a paper on "depression," you could start with an alarming fact about how many people suffer from depression.
Write one to three more sentences that draw on the point you made in the first sentence and connect it to the scope of the paper. For a paper on "depression," this could mean an overview of what depression can do to a person's life.
Decide upon a thesis, which is what your paper will be arguing. This is usually at the end of the introductory paragraph. The thesis states the position your paper holds. Though an informative essay shouldn't state your opinion, it should have a clear point, such as, "Researchers have shown that depression may be caused by three different things, including _______."
Revise your introduction. Add transitions, such as "However" and "On the other hand" to make your sentences flow smoothly together. Edit out unnecessary words or things that slow the paper down. In particular, take a good look at your thesis statement, as what your paper argues may change after you write the rest of the paper.