Here's an example:
I had written a fragment of a scene where Ivy is mad at John because of a misunderstanding. In my head, she is perfectly justified in her outrage because she knows something that John does not, but I didn't know what that might be. I also knew that Ivy was going to be practicing some kind of mountain medicine that John couldn't appreciate, but hadn't the first clue what the treatment would be because I hadn't decided on the ailment she was treating yet.
This is a typical conundrum for a writer. I'll back myself into a corner and until I figure out the whys and wherefores, I'm stuck. I can't write a blessed thing.
But things have a way of working themselves out.
Yesterday, I was googling common Southern Appalachian expressions and came across a reference to people saying someone was "bad to drink". I went on my merry way, and kept writing down other phrases, when all of a sudden in the back of my head, the wheels started turning.
So I start researching home remedies for alcoholism... And lo and behold, what is one of the most common remedies to treat alcoholism? Kudzu Root! And what grows plentifully in the south? KUDZU! So then I research a little more, and what side effect might one experience after imbibing too much Kudzu Root? Chronic constipation!
Wheels start turning faster... So if there's a character who beats his wife and children when he drinks, Ivy might surreptitiously be making him a tonic for his stomach troubles (he's sure to have them if he's a heavy drinker), that keeps him off the bottle, and makes him constipated. Ivy has a good excuse to try giving him more and more "tonic", but then the new doctor comes to town, has no idea about this man's past history with the bottle, and tells this man that Ivy's tonic is useless, pours it out, and gives him something more effective for his stomach, and suddenly all the pieces of my plot come together. :-)
I can't tell you how exilerating it feels when this happens. This is why I write.