Jim,
Say I wanted to write a book about my experiences in Iraq, what am I obligated to keep secret, what can I reveal?
Reply:
I'm not a lawyer. I can't begin to guess what would be legal or not. I'd say that if you had a secret clearance and you knew that some things were classified, you can't reveal that.
Otherwise, If it were me, I'd write about what I know to be the truth. I'd caution you that anything you write you should be able to reasonably prove.
When I write and publish anything I'm careful to set it up so that I can verify it. Readers are a critical lot and will rip your writing to shreds if you can't verify things you write about.
Starting a blog and writing is a good way to begin. There are any number of web sites that offer free space for you to do just that. Google has a good service.
If you do something like that, let me know. I'd enjoy looking in on it.