More to the point, I'm don't think I'd want to be a top selling author. The quality of writing is rearly proportional to the comercial sucess.
However from time to time I do write (and I like to think that some of it isn't crap). But what to write? When? First an idea is needed.
I have some tools and techniques that I use to create the spark, nothing all that interesting, but usually works when I'm stuck for an idea.
Once I have an idea I look at all the possible stories I could tell with that and I start down the path that seems both interesting and challanging to me. But given the same spark another writer would never write the same thing.
So with that in mind here is the brief:
Write a short (very short) story (or whatever, peom, program code, pray) within these limitations, 250 words maximum, must include the word "cubic", must have 2 character (no more, no less), and if you spend more than an hour on it you've taken too long.