The main thing is to have personalities that push forward your story. If you make a character that doesn't fit with the story you want to tell, you will have a lot harder time completing what you want to say.
I develop my characters' personalities based on a lot of different factors, but I first chose character types that would play off each other and create interesting dynamics, as well as further the plot I had in mind and allow me to explore the themes I wanted in my story.
I wanted my story to have themes of identity, family bonds, love, loss of innocence, purity and corruption, with a message of peace, acceptance, and sacrifice. My characters reflect that, and act as foils to each other, encouraging character growth and allowing me to communicate a certain message through their individual arcs.
One character is defined by fear, anxiety, and desire for control, but learns to overcome this by developing a mindset of acceptance and inner peace. Another character wants to fulfill other people's desires and expectations for her, but learns to be true to her self, do what she knows is right, and stop living to please others. My favorite character also goes through an arc of discovering his own identity, standing up for himself, and gaining confidence in his own self-worth and inherent value. So... their character traits come from their roles in the story.
The arcs and traits themselves are based on me, the things I've learned in my life, and on family members, friends, and other fictional characters who have inspired me. :]
My protagonists are siblings, but their personalities are sort of based on two sides of me. To put it suuuper bluntly, it's my introverted side and my extroverted side. By that logic, the siblings are practically polar opposites in terms of how they interact with others and how they see the world.,
If you wanted to look at it another way, it's your basic yin and yang concept. The two black and white sides that can't exist without each other. It's entirely unintentional, and sort of embarrassing for that exact reason, but.. it's uncanny how perfectly it matches.
I have cartoony characters which characters are cliché
and I have more realistic characters.
For the realistic characters I go back to their birth.
I think about their job, how they live, what they have in the fridge,
what they read, what medicine they are taking. Those simple questions
already answer a lot of things which are imporant about their personality.
Character developement is more important than everything else in my opinion,
that´s what makes the characters come allive and able to act on their own.
When you know a character really well you know how they will react when
you push them into situations, like you would also know how a good friend would
react in certain situations
I give them some key traits (Gunhild is smart, Ingrid is polite and shy, Sif is caring, Loki is sarcastic, Thor is dumb yet enthusiastic, Sigrun is bubbly), and I expand from there.
They are me. I come up with characters when I need somewhere to shamelessly dump all my baggage.
And then I give them a bunch of unrelated traits to distance them from myself so no-one would notice and I won't be embarrassed when people read about them 
It's funny, really.
Many comic artists and authors based their characters on themselves, others, historical, mythology, or already existing but popular characters.
However, I never based my MC on anyone. I never think of what to base them on, I just do it. Maybe some of the character's personalities might be based on someone but not by a lot.
My characters all tend to have shards of either myself or my loved ones. Echoing reality in pieces help make a character feel more rounded without it becoming a mary sue/gary stu situation. (At least for my own creation process!) For my villainous characters, I prefer to take inspiration from things that freak me out and affect everyone. (World governments, corrupt science, etc.)
I usually think of a character archetype that would fit a character based on their design. I would also imagine what the character would feel about something or someone.
I rarely create characters one at a time. I usually create them in pairs or trios. I'll typically start with two characters who contrast each other in an interesting way. Errant may be unusual in that it's a reboot of a much older comic with characters I've had since I was in my teens, but my approach actually hasn't changed much since I was a teenager, so they still make a good example.
So, I started with Rekki and Subo. Rekki is short, hot-blooded and energetic, while Subo is big, calm and kind of lazy or passive. They're sort of opposites, but they share common ground in that they're uncomplicated and down to earth, so now we can add another pair of characters who both contrast Rekki and Subo by being more complicated and cerebral, but also contrast each other, so here's Sarin and Jules. Sarin is a moral crusader, intensely proud and very direct in her approach, while Jules is changeable, hard to figure out and takes a convoluted approach.
There are definitely elements of people I know or have known in these characters, but no one character is based on any one person. When describing them, I might say it in terms of relateable people you might know though, like "Rekki is a lad-ette who shouts at football (soccer) on TV, loves roller derby and insists she's straight but would definitely make out with a girl when drunk. She has extreme Spice Girls energy." "Sarin was a drama kid in school. She loves boardgames. Her home is very neat and tidy, but she doesn't own wine glasses and would serve you wine in a beaker." "Subo dropped out of uni due to depression, he has a high-flying older brother who's a doctor he feels inferior to. He's a vegetarian, and he definitely knows who can hook you up with... a certain kind of leaf which he very much believes should be legalised.", "Jules is an autistic dungeon master, they could probably build a working space ship with appropriate time and materials, but still can't drive a car." You probably don't know a super-powered knight who fights monsters with a sword, but you probably know at least one of these people in real life.
I never really thought too hard about this before, but I think I have different 'bags' of characters that I pull from. Some are my most tried and true. I don't really have to think as I write for them because they are character molds that I've used so many times before. Then there is the bag of characters from shows/books/games where i fell in love with them. even though I'm really attached to these characters, I haven't used them in my own writing yet. So it's kind of like I'm saving them for later. And then I have the bag of very experimental characters that I don't have the confidence in pulling off, but I just kind of work on them slowly in the back of my mind. I might do prompts for them, play games using them as the mc, but I won't write anything for them until I'm comfortable doing so.
Of course all of the my characters as well as my worlds are influenced by my personal experiences and the flavor of media that I've interacted with over the years.
I think this is how I operate too. The characters tend to write themselves but obviously I'm drawing from every personality I ever loved and everyone I've met.
I try to explain something I've experienced during my life through them.
Seymon being the MC has slowly become a very personal character, Stephanie and Salamon are based of all of my friends but focusing on different aspects while adding flaws to both of them and Seymon.
Then there's Hotdogiano, which I made when I was hungry on elementary...
Through actions! I have a basic idea of what they're like, and then I write them responding to different situations. Then I take a break and look over it again, to see if it changes how I see them. You really don't know who anyone is in a vaccuum, it's all about how they respond to different circumstances.
I try to make them stand-out from each other, although I give them small traits that allow them to connect. Traits that make people people wanna analyze/pick apart the character some more and theorize possible interactions with other characters that they never get to meet.
I use real people as a reference, not as self-inserts but just look at how people interact to further expand my characters personalities
Generally for my writing the characters take back stage to something like an environment or idea, in a reductive way they're only there to be punished. Also I very much of the philosophy a work of art should exist outside it's creator - be allowed to grow and develop as it's own.
As such characters often start off as a piece of the story puzzle meant to fill a role, the base personality is somewhat connected to that role and develops based off what feels most natural given whatever conflict I toss their way.
For my characters, I usually decide on a distinct character personality they would have. Like my main character is Juvia Elias, and she is a person with low self esteem and also a loner. So I would always think what would someone with that characteristic would do. Sometimes if I'm not sure, I find shows and movies that have those type of character and take inspiration from that.
1 month later
closed Apr 26, '22