I’ve been thinking about this topic and have come to the conclusion that I really haven’t a clue where my ideas come from. Somewhere inside my head, I think, as I don’t recall any specific ‘triggers’ for any of the stories I’ve written.
I start with a very basic scenario – a kind of short ‘blurb’ that you might send in a query letter. Two people with a problem (or problems) they have to resolve. For a story to work (at least, to my own satisfaction), I have to empathise with their problems and I have to feel very involved with my characters.
The twists and turns in the plot don’t come from any external triggers either, they come from the characters themselves. And even if I’m not in love with my hero to start with, I have to fall in love with him while my heroine is falling for him!