Many of my ideas come from my overactive imagination. I have a tendency, a very rude one I guess, to watch people and imagine what there life is like outside of the moments I see them. I ask myself questions like, what if he is a vampire and is on his way home to find his father dead, slain by a werewolf? Or what if that girl is an undercover agent trying to find who killed her partner ten years ago?
I had a friend who used to write short stories almost everyday because that is what she dreamed about. I personally wish I had dreams that were good enough to write down for stories but unfortunately many of my dreams are pretty dull.
I have another close friend who likes to take characters from movies or television shows and throws them into the world he has created just to see how they would react. Personally I love this idea! I like using actors pictures as a way to keep my character descriptions and personalities accurate throughout the book I’m writing.
Surprisingly fun story ideas can come out of just creating a new character. When I hear an interesting name I always put it in my writing notes to start a new character, just the name alone starts my creative brain thinking about personality, physical descriptions, and their life/love experiences. Creating this character usually starts bringing out ideas for a new story and the nice thing about this method is my protagonist is already created when I start writing.
A great prompt is also using pictures of places to start a story. There are so many great pictures out there of real castles or imaginary space stations that an author can through characters into to start a story. Name the place, create the fantasy rules, fill it with characters, and start your story.
Another great source for story ideas are writing prompt websites and apps. A great book I love, not only for prompts but writing tips as well, is called the 3 A.M. Epiphany by Brian Kiteley. Not only does this book help with ideas but helps with writers block while helping improve character depth. Great book!
So start creating that world, getting those creative juices flowing and keep writing!