Well, not really advice per se, but this is some good stuff Christie wrote in the introduction to her novel Passenger to Frankfurt. I loved it, and I thought it worth sharing.
The Author speaks:
The first question put to an author, personally, or through the post, is, "Where do you get your ideas from?"
The temptation is great to reply, "I always go to Harrods," or "I get them mostly at the Army & Navy Stores," or, snappily, "Try Marks and Spencer."
The universal opinion seems firmly established that there is a magic source of ideas which authors have discovered how to tap. One can hardly send one's questioner back to Elizabethan times, with Shakespeare's
Tell me, where is fancy bred,
Or in the heart or in the head,
How begot, how nourished?
You merely say firmly, "My own head."
That, of course, is no help to anybody. If you like the look of your questioner, you relent and go a little further.
"If one idea in particular seems attractive, and you feel you could do something with it, work it up, tone it down, and gradually get it into shape. Then, of course, you have to start writing it. That's not nearly such fun--it becomes hard work. Alternatively, you can tuck it carefully away, in storage, for perhaps using in a year or two years' time."
A second question--or rather a statement--is then likely to be, "I suppose you take most of your characters from real life?"
"No, I don't. I invent them. They are mine. They've got to be my characters--doing what I want them to do, being what I want them to be--coming alive for me, having their own ideas sometimes, but only because I've made them become real."
So the author has produced the ideas, and the characters--but now comes the third necessity--the setting. The first two come from inside sources, but the third is outside--it must be there--waiting--in existence already. You don't invent that--it's there--it's real.
You have been perhaps for a cruise on the Nile--you remember it all--just the setting you want for this particular story. You have had a meal at a Chelsea cafe. A quarrel was going on--one girl pulled out a handful of another girl's hair. An excellent start for the book you are going to write next. You travel on the Orient Express. What fun to make it the scene for a plot you are considering. You go to tea with a friend. As you arrive, her brother closes a book he is reading--throws it aside and says, "Not bad, but why on earth didn't they ask Evans?"
So you decide immediately a book of yours shortly to be written will bear the title, Why Didn't They Ask Evans? You don't know yet who Evans is going to be. Never mind. Evans will come in due course--the title is fixed.
[I know that Christie's comments about setting won't apply to those of you who write SF/F, but a lot of this rings true for me. Discuss.]