A funny thing happened to me yesterday. I posted in the thread What do you wish SK would write about?, half joking. Then I got an idea and started writing my own story on the subject I'd jokingly suggested. I wrote a rough draft or outline of an entire story, very short so far. I didn't worry about certain issues, the important thing being getting the essential idea on paper (as it were). Usually I have a problem deciding on a conclusion; this time it was easy. The story told me about itself and how it wanted to end.
Now though, I know it needs to be fleshed out, and probably a lot. After all as is, it's all of 1 1/2 pages. Being as amateur a "writer" (ha) as a person can possibly be, I have no experience, other than having read other great authors which I can use for mentoring purposes, "fleshing out". But, I'm kinda excited because I think I just might be able to create a monster that has life.
That's how you start. Good for you, Blunthead!