If the real world is full of different people, why shouldn't fictional worlds be the same?
Answer: because trying to fit something as big and busy as the real world (or something akin to it) into the head of one individual person is a very big ask.
Trying to create a character who is nothing like you is easy enough - it's just a pile of personality traits, a few quirks, maybe a messy backstory and guilty cookie-related secret or two. Trying to make them come to life according to those criteriam is hard.
Handling of complicated, dissonant characters can take a huge toll on the quality of a work; be it a roleplay using canon characters, a high-end piece of fanfiction, and, most of all, original stories. You know exactly how you want them to be, but blast you if you can make them! Your own personality and moral coding creeps too much into the narrative, affects it, and results in something far less stellar than you'd hoped for.
Your tough and dependable warrior freaks out at the sight of blood like a teenaged girl.
Your unprincipled thug is utterly incapable of saying anything ruder than "idiot".
Your super-genius doesn't know a quark from a neutron.
And to top it all off, you think the horse might be developing views on animal rights.
However, the situation isn't totally irrevocable. And don't worry, I'm not about to start off on a spiel about life experience. That's not fair. Not in the least because I doubt anyone's ever going to be able to meet a seven-hundred-year-old retired god of chaos to meet over a cup of coffee and chat about accurate portrayal of his personality. I'm not even here to suggest peoplewatching entirely; as interesting and insightful as it can be, sometimes it just feels like being a creeper. And when you're trying to pound out a novel, you've hardly got enough time to go out and hunt through the supermarket for someone to watch as comparison for the behaviour of your narrator's neurotic second cousin.
What I am here to suggest is . . . thinking. And reading.
Two horribly arduous tasks, I'm sure.
When hashing out a character, if you're not in favour of random situation generators that you can plonk them into to have a play with and start them out that way, it's always useful to turn your mind inwards and think about the situation at hand. Think about all the options ANY person could take - whether or not they match up with things you would do is a different matter. Pick the one that best fits the character and, no matter how out of kilter it feels with your own views, make them do it.
Remember: the character isn't you. And it's all for the good of the plot. Honest!
In terms of reading, well, that's fairly self-evident. If the story is something of a genre you've not written before, then go and give the genre a good poking, maybe get some recommendations from its fans for good starting points. If you want a good example of how to pull off a certain character archetype, go for a book or genre that you know does it well.
You may not ever be able to fully think like and behave like the character yourself (which, in some cases, is probably a good thing) but reading books critically, with an eye on their behaviour and thoughts throughout the action, can help you out over the more questionable areas in your own story. Your uber-cunning court lady is highly unlikely to make the blunder of falling for the "spell ICUP" joke, however funny you think it is.
And now, before I go, I'm going to leave you with a few articles I hope you might find useful just for general perusal when dealing with characters suffering from Wonky Personality Disorder:
- Tips to keep your "badass" from being just a plain "ass".
- Tips on how to realistically portray victims of abuse.
- Tips on how to write more "masculine" members of the male species.
- Tips on how to write them clever types.
The site that I borrowed these from - "Springhole" - also does a really good series of things for both original fiction and fanfiction characters, as well as squillions of generators, articles, and other forms of epicosity.
~ Charley R