What is the name of your state? California
I am pitching my true life story idea to various authors and book publishers. What kind of legal protections do I have? What kind of precautions should I take to protect my story and idea?
Your worry should be less about protecting your life story from being written by someone else and more about protecting yourself from a lawsuit arising from the contents of the story you write.
Those people who have played roles in your life will be either identified by you or identifiable by content. There can be defamation and invasion of privacy (false light, publication of private facts) issues when writing stories about your life.
I suggest you visit the following Knight Community News Network website -
http://www.kcnn.org - and look for the "legal risks module." Although the site is designed for online writers, the legal risks advice is good information for all writers.
Once you have written your book, I recommend you have your manuscript personally reviewed by a publishing law professional in your area, for the careful editing and tweaking of your text.
A traditional publishing house will have editors but you will want to approach any publisher with a polished product, this after communicating by letter with the publisher about your book.
Do not send any work to a publisher without an invitation from the publisher to do so. Having an agent can help you get your manuscript read. Unsolicited works are either returned to the author unread or tossed in the trash unread.
Good luck.