Characters done well have a life of their own. We know them, often better than we know the real people in our lives! If we were to drop Hermione Granger on the U.S.S. Enterprise, or give Arya Stark a job at Starbucks, we have a pretty good idea of how they would react.
That’s what you need for your characters. Not just the main character, but all the major players in your book: the villain, the main character’s best friend, their parents... everyone who has any sort of significance to the plot needs to be fully fleshed out.
Every author is different, but generally speaking we all ask our characters some questions, from the doozies to the frivolous little details. This is how I go about creating my characters. Usually I have a notebook dedicated to the book/world, and six pages for each character. Each page covers a specific aspect of the character: their core, their personality, likes and dislikes, abilities and disabilities, background, and physical description.
And these are the questions I ask:
The first Dragons, Zombies and Aliens blog was started in 2015. Somewhere between college coursework, paying rent with door-to-door sales, and keeping up with my sorority sisters, I wrote reviews, rants and commentaries on books, TV shows, and movies. Now, this blog has moved, improved, and the sky's the limit!