For long term projects such as novels, I have always found it a good idea to set up a mock interview to develop your characters. It always helps to flesh them out beyond words on a page and sometimes asking slightly difficult questions, even completely unrelated to the story, will help you to develop them as a person and shape their direction within the narrative. Basic questions I tend to ask include the obvious:
* What is your name?
* How old are you?
* Where were you born?
* Are you married? Do you have children?
* Where do you live?
We could come up with an endless list of these basic questions but what really helps me to give my characters definition out is asking something a little more intimate and engaging:
* What is your greatest fault?
* What is your greatest virtue?
* What is your happiest childhood memory?
* What is your earliest memory?
* What are your personal feelings toward [insert another character in the book]?
* What did you want to be when you were a child?
* What is your favourite quote/poem/song?
Or something a little more abstract:
* Would you rather be a brick or a house?
* Would you rather be a river or an ocean?
* Do you prefer sunset or sunrise?
* Cats or dogs?
And perhaps even some really penetrating or difficult questions:
* What is the single biggest mistake you have ever made in life?
* What is your proudest achievement?
* Do you have anything in your past you are particularly ashamed of?
* What would be worse than being dead?
Do not merely impose your own views, beliefs and opinions onto this character. In order to truly create a character you must let him or her express his/her own feelings within the context of their personality, even if you might find those opinions to be the complete opposite of what you personally believe or even abhorrent to your own beliefs.
Nor must you restrict yourself to the beginning of character development. The exercise of going back and asking complex or specific questions can sometimes help in a particular tight spot when you are not sure how your character might act in a given situation.