That's a good question! I'm lucky that I have a lot of ideas come to me. The tricky part is turning those great ideas into a minimum of 40,000 to aim for a novel. Otherwise I can belt out a short story from them.
The best way to find inspiration is to look at people and places around you. Take a walk through the mall or in the park. Become a people watcher.
As a mentalist, I am a natural people watcher and I find myself creating character sketches from the people I see. Sometimes I create secret identities for them, similar to Indiana Jones, Miss Marple, etc. When I have a character in mind, I ask myself, "What would happen if this person were to ......." and that's when the story comes.
Other times, I may be watching the news and think, "What would happen if...." and that is how I started my current work in progress.