First of all, write down all the things in your life so far that you think are important. Spend a good bit of time on this. Next, you must ask yourself what sort of order you want your book to be in - do you want it completely chronological, or do you want to begin with a "climax" in your life and then go all the way back to the beginning so you can lead up to it? This is important, as it changes the mood and style of your book. Another thing crucial to your writing is whether you want it to be overtly funny, deadly serious, or somewhere in-between. Once that's sorted, look over your life events again. Is there anything that stands out, just waiting to be written like a comedy sketch? Is there something dramatic in your life that will help the serious tone of your book? Once these are sorted, you are beginning to give life to your idea. Hope this helps.
When you say "a story about myself," do you mean a memoir? Or a story closely paralleling something that's happened in your life? Or a story where you (or a similar you) is the MC, but fictional things happen? I'm assuming that you probably mean memoir, in which case, the question is: What have you experienced that is so significant that others will find it compelling or that compels you to write about what happened? That's where you should start.
you start the same way you'd tell a friend about what happended to you yesterday... the only difference is you write it down, instead of saying it aloud... but if it helps to pretend you're telling your friend about your experience, then go ahead and say it out loud, as you write it down...
