There are 3 basic steps to an introduction:

1) Hook - get them interested but be honest:  don't hook them with a red herring!

Use one of these tried and true approaches: 

-statistic or intriguing fact -- this requires a little more leg work but is often worth more bang for the buck.  Search your topic in statistics, news, science, trends...

-quotation -- there are so many available online.  Try the website Brainyquotes

-sassy assertion/observation -- this is for the more confident writer who has something to say themselves.  It is like the previous approach, but here you will use YOUR words of wisdom or a bold statement.  

2)  Background - the who, what, where of essay (titles, authors, characters, theme stuff go here)

This is usually 2-3 sentences that bring the reader up to spend.  Assume they know the text but not your purpose or focus.  

3)  Thesis - the actual purpose of the essay, the "theory" you are supporting 

This is the claim around which all else revolves.  It belongs at the end of your introduction.