well, you should start at the beginning. I mean, when trying to write, I think the key is to write something, anything down. It doesn't have to be good or interesting, it just needs to be on paper, and from there, you should be able to find a story. Of course, this is just how I do things, and won't necessarily work for you.
After writing something down, I often have someone read it. Feedback on what I have written is often helpful, even if it is hard for a little while.
418 I'm a teapot