I am an amateur writer wishing to publish my work later in the future. I hope that my advice can help to some extent.
1) Draw from real life inspiration.
My favorite thing to do when I’m out in the public/crowded area is to observe people. I screen through everyone in my view, noting of their physical appearance (young? old? attractive? a minor ethnicity? clothing?), their manner (calm? joyful? aggressive?), their attitude and talking style (if they are talking. e,g: accent? word choice?). Same with people in my working setting. While these common people may seem boring, they can be surprisingly inspiring. (I have one short story that was based on my part-time job). Your family members and friends can work as a source of inspiration too.
2) Wikipedia and newspaper/articles
No joke, but I like reading Wikipedia articles, as well as miscellaneous articles from various sources (Reuters, The Daily Mail, VICE, etc). These infinite amounts of articles give me materials to work with ideas, especially stories about historical figures. Lessons from the past can lend a helping hand in writings.
3) Dive into fields that are not in your expertises
Sometimes, discovering a new field can give you new ideas. It might be discouraging at first since you don’t have background knowledge regarding the field, but the more you read, the more your perspective will open. For example, I have some background about life science, but I always like reading about politics, history, psychology (I’m pursuing a minor in psychology too) and economy. Sometimes, I read about physics and arts too. I notice that enriching your knowledge with various fields can help.
4) Talk to people
Real life people are complicated and multi-faceted. Because of that, they can also be a rich source of inspiration (e.g: con artist Frank Abagnale, WWII double agent “Garbo” Juan Pujol Garcia, FDA’s Dr. Frances Oldham Kelsey or maybe your next door neighbor). Try talking to them, get into their stories, their mindset, their decisions and perhaps you can get some new ideas to draft on.
5) Questioning the meaning of your work
This is an additional idea, but I usually redraft my idea in my head, questioning the deep meaning and symbolism behind the story. Even if I just wrote a scene out of a burst of creativity, I will still come back to redraft the idea in my head, wondering if I can add more depths and symbolism into the story.
One of my most used questions is: What morality I’m trying to tell a story about?
I hope these little advice can help you. Happy New Year and wish that you will always cultivate great ideas