How I get my ideas and how I turn them into stories.
Sometimes an idea can be sparked from seeing or hearing something. A tip you hear a lot is that you should carry a notebook around with you wherever you go. I have always done this, but sometimes my notebook is an app on my smartphone.
Sometimes something you watch or read can spark an idea. If it relates to established characters it can be followed up on through fanfiction, alternatively it can be done as original fiction.
An image can spark a story idea.
Music can affect your mood, it can also help with idea, if not for a whole story, it can do so for scenes within a story.
There are no shortage of websites and books out there that offer writing prompts. These can be ‘first line’ or scenario based.
If you search the forums at Nanowrimo.org you will find story adoption posts, ideas that people came up with, but never followed through, available for the taking.