I've never had a character come to me fully formed and ready to go. They come to me like ghosts and I have to make them real by getting to know them over time. Creating (good) characters is hard work, but when you take the time and effort to make them 'round' it's always worth it.
So what is a 'round' character? E.M Forster wrote in Aspects of the Novel, that:
The test of a round character is whether it is capable of surprising in a convincing way. If it never surprises, it is flat... It has an incalculability of life about it - life within the pages of a book."
Someone once told me that if you can imagine the character existing outside of the novel, if they have lives that reach beyond their role in the book's plot, they're round. It's all about putting life back in those ghostly figures that first appear.
But it's not always so easy to create a round character. One approach is to let the characters reveal themselves to you, to really sit down and get to know them.
Write out a set of questions for your character and conduct a kind of interview. This gets your brain thinking about all sorts of random details that you can use for background info to help round out your character. If you're not sure what to ask, check out this list of possible questions.
HINT: This works even better if you don't know the questions beforehand. Have a friend do the asking - it'll keep you on your toes!
Have a chat.
Imagine physically meeting your character for the first time (maybe in a cafe, or at the library - it depends on the character). How does the conversation begin? How do they respond to you? This is great for picking up body language and visualisations about the character.
HINT: It's not recommended to tell people who aren't writers that you've been 'talking with your characters'. They just don't get it. Believe me.
Fill out a job application.
This idea comes from an article on The Write Practice. It's a great way to work out the facts about a character. Don't forget the important yet sometimes over looked details like age, date of birth, and previous work history.
HINT: As the article says, don't hesitate to add more parts to the job application and really scrutinise your character.
Write a letter.
Not many people write letters anymore, so this is a great way to learn more about your character's motivations, their past, their friends. It's a good exercise for creating tone and voice as well as vocabulary.
HINT: Check out this writing prompt we set up a while back for more ideas on what to consider when writing your letter.