Authors have different ways to attack writing. I thought I would share the approach I took for the newest book, Ancient Tombs and Spells.
The inspiration: a prompt from a fellow writer in my writer's group. Wealthy man is dying (or not) Man Servant is feeling sad and guilty (for some unknown reason). This being rather ambiguous, left lots of options. I liked the idea of a wealthy man dying ...maybe murdered? Man Servant? Seemed boring or obvious....how about loyal cat companion?
Now I have two characters, what do I do next? Maybe the cat companion wants revenge. Okay, so how does it do that? Maybe it (he? she?) can uses magic. Hmmm, mystical cat might need some help if (let's go with he) has been spoiled by a wealthy lifestyle and not used his magic. So I decide he must request help for an evil spell from another cat that knows about magic. 
Now I have three characters: Wealthy Man/ spoiled cat companion/ cat who knows magic and evil spells. Suddenly my mind goes to Egypt. It has always been a fascination to me and I recall a history about cats being worshiped as gods. If I am going to write about cats and Egypt, I need to know facts. Even if I make up things, they need to be based on facts or they won't make sense or be believable.
Searching the internet is helpful. And Barnes and  Noble - a  cappuccino in their cafe always helps my thoughts. Low and behold, there just inside the entrance, is a beautiful big book on Egypt. Encyclopedia of Egypt, full of facts including a history of cats and even pictures of their burials. And I discover Saqqara, a known place for cat and other animal burials as well as the famous Step Pyramid. Now I have a setting for the story.
Then another character shows up - Cattutkin, a smart Egyptian cat that can tell the history and lead them through the ancient burial grounds. From there it was all fun. Wealthy man (Winston Carrington Thornbridge the Fourth ) cat companion (Marcos) fellow cat who knows evil (Simone,  black, elegant, French), and Cattutkin, their Egyptian guide.
The cats took off and I had a hard time keeping up. I often didn't know what they were going to do next. They were delightful with their surprises. So, they filled pages with their antics and led a merry chase for 30,000 and some words. I hope readers love their story as much as I did writing it.       READ DESIGNING THE BOOK