Your introduction is the key to grabbing the reader's attention and giving them just enough information to keep them interested and let them know what they will be reading about. Your introduction will start out with an attention-grabbing sentence - a "hook" sentence - about your topic. Be interesting, but don't give away the whole idea in detail right at the beginning.
Your next few lines will be a little bit more specific, aiming to set up enough background/context on your topic for your reader to be able to follow your ideas later in the paper. Avoid including quotes or citations in the introduction; any summarized concepts or other ideas in this part should come from you.
The last line of the introduction will be your thesis statement. This line will be very specific, letting the reader know your position on the topic and exactly what you will be discussing (often in the form of one main idea and three sub-points).
Think of your introductory paragraph as an inverted triangle: starting from the general and moving towards the very specific. You may not need to have all five sentences as laid out below, but be sure to have your hook, some background information, and your thesis statement in your introduction.
Check out this presentation by our Writing and Grammar Tutor Claire Pienaar about how to write an introduction paragraph.
Introductory Paragraph Example from Claire's presentation
Even though Christopher Nolan’s Batman has been critically acclaimed, the fact remains that the most successful Batman ever made was Tim Burton’s version starring Michael Keaton (Aspen). Since Batman’s comic book debut in 1939, Batman has been portrayed in the 1960s hit television show (starring Adam West) and in a number of feature-length movies, with A-list actors such as Michael Keaton, George Clooney, and Christian Bale starring in the lead role. Though all of these actors brought their own unique style to the caped crusader, Michael Keaton’s performance stands out among the others. Michael Keaton’s comedic timing, on-screen presence, and ability to deliver flawless lines makes Keaton’s version of Batman one of the most effective on-screen portrayals of the character to date.
Example from Kibin.com
Background and context