main idea and give youressay purpose. 

In addition to stating your main idea and purpose, it is always good to give the reader a little "preview" of the topics you will cover.  For example, if your formative experiences have made you an outgoing and athletic person, the topics you will want to develop are the experiences that made you this way, and those topics should be mentioned in the introduction.

If you begin with a statement about your personality now, share your purpose of exploration of your "roots" as this person, and offer the reader a preview of how you will develop and support your main idea, you will have a introduction!   

There are several ways to open an autobiography. Before you start, there are two key things you will want to keep in mind. First, an opening paragraph is crucial to any piece of writing: you will want to say something compelling that will keep people reading. Second, as in biography, you want to think first about the main point you are trying to make about yourself. Definitely avoid simply throwing out a mass of facts—these facts, while important, need to connect to and support a central idea or theme.

Once you have an idea about what makes you who you are, you can choose from several tried and true opening gambits. One is to start in media res, or in the middle of the action, perhaps at a crucial point in your life journey when everything is hanging in the balance. You could also choose to start with a startling or unusual fact or story about yourself: that is a very common (and often successful) way to hook a reader into wanting to know more about you. Another idea is to begin with a descriptive passage that puts a reader into scenery of your life that is significant to you. Finally, you could begin very prosaically by explaining why you are telling your life story.

It can be helpful to look at other people's autobiographies or memoirs (a memoir is very similar to an autobiography but is not necessarily a complete life story) to see how their opening paragraphs set the tone. Some examples that can be found online are the works of Benjamin Franklin, Frederick Douglass, and Helen Keller.

The introduction to an autobiography sets the stage for the life story to follow. As such, you could use several different approaches in writing your introduction.

If the autobiography is going to be strictly chronological, the introduction would set out the initial facts. Ex: I was born on Jan. 1, 1990 at 2:23 AM. My parents knew, from my first screaming breath, that I was going to be a night owl and a challenge to control.

A flashback technique could be used if you wanted to introduce a highlight of your life, then go back and tell how it came to pass. Ex: As I strode to the podium to deliver the valedictorian's address at Commencement, I thought of all the nights spent studying, all the parties missed due to assignments I was polishing. All the work was worth it at that moment. It started in kindergarten. I got a gold star for every letter book I completed, and I loved those stars.

Writers often begin with what is termed by Bailey and associates in The Practical Writer as a "motivator"; namely, some idea or question that will intrigue the reader enough that she/he will eagerly continue reading. Now, motivators can be several things:

• A motivator can be a question relative to a broad idea or a particular idea.
• A motivator can be a reflection upon the meaning of an abstract or concrete concept
• A motivator can be a quotation that is relative to the rest of the paper.
• A motivator can be a little-known fact or statistic that is relative to the paper.
• A motivator can be a pulled passage that centralizes the idea to be the focus of the paper.

So, in writing an autobiography, the writer can use any of these types of motivators, or, since an autobiography is a narrative of sorts, the author can begin with a significant episode (a pulled passage) in his/her life--beinning in media res, so to speak--and focus the rest of the narrative of his/her life around this significant moment.  If one chooses to use such a flashback of a meaningful life event, he/she should carefully select one that is a bit curious/puzzling/interesting, yet thematic to the rest of the autobiography.

Perhaps, there has been a point at which one has had an "ephiphany" of sorts, an alteration of perspective on life. For instance, one could write something like this:

It was not until I was ---years old that I understood the meaning of my father's words, "_____________"
OR
It was on a particularly dreary, cold day in January when I was ___years old that I first discovered real sunshine in my life. 

As another choice, if using a quotation, choose one that is existential, or philosophical.  Here is an example of one that could have an extensive meaning:

"A man's errors are his portals of discovery."

As a final idea, browsing through introductions to autobiographies of famous people (there are many in any library or book store) may help in generating ideas for an intriguing beginning. See the link below on writing an introduction for additional ideas. After reading all these ideas, taking a walk really helps to put ideas together and even generate new ones.