An introduction in a piece of text is the opening statement(s), and is the piece's advertisement. The introduction tugs the reader into the text and has four basic elements. Here's an outline format of an introduction. Note: This is for an expository essay. The basic essay is always expository. Will not work for a fantasy tale.

I. Introduction
[indentation]A. Lead
[indentation x2]1. Attracts reader to text.
[indentation x2]2. Three kinds of leads.
[indentation x3]a. Questioning Lead
[indentation x3]b. Arresting Lead
[indentation x3]c. Quoted Lead
[indentation]B. Topic Sentence
[indentation x2]1. Gives reader information on writing piece.
[indentation x2]2. Give basic information. Do not reveal anything about subtopics.
[indentation]C. Hints at subtopics
[indentation x2]1. At least one per subtopic.
[indentation x2]2. Not directly said, but meshed in with either the topic sentence or the lead.
[indentation]D. Transition to first Body Paragraph

A, B, and D all have to be in order, but C is meshed in with either A or B, so you do not need to worry about placement for the hints at subtopics.

There are different kinds of leads. Three, to be exact. I should enlighten you on their meanings.

Arresting Lead: Makes the reader stop and think. Something clever and catchy.

Questioning Lead: Asks the reader a question, making the reader ponder and read further to find an answer.

Quoted Lead: A lead involving a quotation from anyone that directly relates to the topic of the essay. Something that does not come right out and name the basis of the topic, though. Makes the reader think.

The transition can either be at the end of the introduction or at the beginning of the first body paragraph. Fluently brings the leader from the introduction to the first body paragraph without a major jump from place to place.