Q is for Question.
There is one question you must ask yourself when you create a character. Every decision he makes in the course of the narrative will hinge on the answer.
What does this person want?
Goals and wants are not necessarily the same thing. Your character can have goals, be they professional or personal, and they could be miles away from what he truly desires. Different people want different things, and the goals they set will help them achieve them (or possibly not).
Circumstances may tear a character away from what she wants most. In Eric Knight’s classic novel Lassie Come Home (1940), our heroine is sold to the Duke of Rudling and taken far away from Joe, the boy she loves. She misses him so much that when she escapes, she sets off on a dangerous and harrowing journey from Scotland all the way to Yorkshire, and home. I absolutely adored this book as a child and freaked when I managed to find a copy.
A character’s wants can also blind him to his moral path. Twisted desires are the focus of many a tale. Consider Boromir from The Lord of the Rings: The Fellowship of the Ring. He’s the jock hero of Gondor, its most decorated warrior, and the favorite of his father Denethor.
Boromir’s desire to save the struggling kingdom of Gondor colors all his thoughts. He wants to save his people. The Ring senses this and tries to exploit it, knowing how close Gondor is to Mordor and from there, to the hand of Sauron.
The closer the company comes to actually carrying out the purpose of the Quest, the deeper becomes Boromir’s torment as he tries to justify to himself actually taking the Ring from Frodo. At Amon Hen, he finally gives way to his desire, breaking the Fellowship.
The Ring used Boromir’s wants against him. But in a way, Sauron’s desire to possess the Ring of Power (and his failure to realize that a tiny hobbit held the key to his doom, not the mighty armies of his enemies) blinded him to the other characters’ purpose in destroying it.
While some characters want things to change, others want them to stay the same. Mrs. Hudson, Sherlock Holmes’s landlady, would probably like a quiet house and a tidy tenant. Instead, she gets someone who plays the violin (screech?), does smelly, messy experiments, and has all manner of people traipsing in and out at all hours of the day and night.
Bilbo Baggins in The Hobbit also wants a nice quiet life, but Gandalf drags him into the Quest of Erebor and he ends up quite a different person from who he was when he started. You might start out with your character pushing toward his desires at the beginning of your narrative, but as in life, the paths of the best stories wind and twist and rarely go anywhere in a straight line.
Ask your character this question. Listen to what he has to say. You might be surprised by the answer.