Sometimes it just flow. For me, sometimes when I listen to a song, a scene has come to my head. So I can make a one shot story, or part of a story. After that, if I got the feeling, I'll make a story from it.
I take inspiration from books, movies, or TV shows. I also take inspiration from idols, concepts, and mvs/songs. I have always had a big imagination so coming up with story ideas isnt an issue (my bad memory and not knowing what i wanna continue the story with IS an issue on the other hand )
I am writing a story rn. Its a murder mystery, the three main characters are based on idols (Yeonjun TXT, Jisung Stray Kids, and Hayoung Fromis_9). Tbh I mostly draw inspiration from idols for character design. Im plotting the whole thing out down to the witness statements, police files, and who did it where, when, and how. If you wanna find creative ways to keep your story interesting, I recommend looking over it and analyzing it from a viewers perspective. Thats how I try to make my ideas more original and how i make sure nothing is too predictable or cliche. For making a story, I recommend looking at media, or people that give you inspiration or something thats interesting that you can make story out of.
I think fanfic ideas really emerge from real stories and books that I read. Other fanfics that are of amazing quality also inspire me a lot and give me a bar to shoot for. I'll write the steps I usually take to think of a plot/story/idea for a fanfic.
1. Which group/idols will be included? This is key when writing a fanfic. It's actually why I think writing fanfictions is easier than writing other creative writing because the character design and general dynamic is there for framework. Of course you can change it based on what plot/AU you're using, but stuff like "Ten (NCT) hates fruit and Kangmin (Verivery) is the maknae" won't change and it can really help you build the plot around what they do.
2. What setting/AU do you want to use? Your fanfic can be a College AU (very common), Sci-fi AU (common, especially for ATEEZ), Spy AU, Assassin AU, Royalty AU, Superpower AU, Soulmate AU (careful with that one, it can turn out forced), and Canon Compliant.
The universe you choose is essential to the whole story, obviously, so I think just choose something that you're comfortable writing about. Realistic fiction is by far the easiest genre to write, but if you're looking for a more investing work and a unique opportunity, the other AUs I listed are only some of the most common ones, with many more.
3. What type of story? This one is relatively simple to be honest. by type of story I mean if it's romance, betrayal, "Dead Dove Do Not Eat", Non-romantic action, etc. The possibilities are endless, and the audiences for each and every one are great too. Also a part of this step is deciding if it will have a happy or sad ending (oml wtf is wrong with those fanfics about t*rturing and k*lling idols). So come up with this before delving into the plot because then there is at least a basic framework to work with.
4. Plot? Simple way is actually very simple: Think of 5 books/stories that would fit your type of story. Take one element from each. Mix it up. Tweak it with the personalities of the characters. Add some of the ideas you've had brewing in your head. Boom. Inspiration + Original.
Super simple way: Take a story. Replace the characters. Alter the storyline. Rewrite it in your style. Boom. Give credits and done.
Hard way: I really have no comments on this one. You can try to come up with your own story and build your own universe and stuff. Either way, you should probably use an existing story as a simple base and as the storyline thickens, the piece that it was inspired from is overcome with the own ideas and originality present.
And that's about it. A really good way to get inspiration is from other fanfics. Archive of Our Own is an amazing fanfic site with a lot of long and good quality fanfics in my opinion.
If you don't like my advice, I don't really care (I'm a 13 year old giving writing advice wtf) but I do hope this helps. ^^
As someone who has written a multitude of fanfictions, I have to tell you that most of the time my best ideas come when I'm not even trying to think about what I want to write however, here is some of my best ways to break down how to actually write a fanfiction: Book/Movie Based?
1. Is your plot going to be loosely or very based around a book/movie plot? Great! Absolutely nothing wrong with that
2. If it isn't, then nothing wrong with that.
I personally prefer coming up with my own concepts but a lot of people do take ideas from books and movies and that's absolutely okay to take inspiration, do not feel bad if you do!
Idol Fanfiction/Fictional Characters/Movie Characters?
1. Idol Fanfiction - Who are the groups/idols included - are they going to be like the actual idols or reworked completely? Different ages, personalities etc...
2. Fictional Characters - Name, Age, Backstory, Importance, Personality etc need to be considered here.
3. Movie characters - Very similarly to idols consider if you want them to be completely the same or different.
Plot
1a. Go back to the first point if it based on a movie/book maybe take some time to go back and watch or re-read said book and take notes on parts you think you can utilise
1b. Fill in any gaps in your plot with things you personally find interesting, maybe you'd like to mix the storyline of two books or you can just fill them in with anything you can think of that works
2a. If it isn't book or movie based then personally what I enjoy to do first is brainstorm different ideas, what is interesting, what different concepts can I come up with.
2b. After coming up with a basic concept I enjoy to highlight the basic outline of my plot so that if I ever get lost in what I'm writing there's something I can refer to know where I was wanting to go with it. Any basic outline can be rewritten as many times as you like through the time you're writing.
Characters
1a. If they're based on real people- while maybe you don't want to base everything off them, you can certainly to inspiration from that person's habits and personality
1b. Outline the importance of this character in the story and what you want them to do basically so that you know where this character is going.
2a. If it's a fictional character then you can of course pull inspiration from other fictional character or just have them very loosely based off someone you know. Honestly wherever your mind can take it, follow it. Creativity is key to creating characters and plot.
2b. See point 1b.
Setting
1a. Where do you want to have this take place; a school, a hotel etc...
1b. Is this going to be based off a real place? If so maybe have a picture of said place up so you can take inspiration
2a. If not based on a real place, again have a basic image in your mind of what you want it to be like and just follow it through to a point where you're happy with it.
I write down any ideas I have on my computer. It's usually phrases but you could write a one-shot and incorporate that into your story. For me, I go with the flow. Whenever I'm feeling emotional or down, my character will feel emotional and down. If I feel happy, then the character will be happy. It's basically a self insert, but a completely different person than me.
See I Don't Write Fanfic's I Write Stories And One This I Noticed. Is You have to Love What your typing about or writing Which ever you Prefer. But You Have To be Drawn To it. Also Have to Know the Character Or Person either by Research Or Just Any Information. And Almost get into their Head, Or Know Their Personality But in your Cause On Camera. You Have To Just Like what Your writing About.