If you're still working through your first novel (like me), I would recommend choosing a story that is purely driven by a character motivation or need i.e., pick a character with a clear goal.
A goal will help set the rest of the story in place. If your character stays on his/her path, pursuing their goal, then you as the writer will find it easier to move forward.
Remember that 'focus' I was talking about? If you focus on your main character's goals, you may find it easier to write every scene in service to that quest. Look at every scene as a way to bring your main character closer to achieving their goal.
Haven't got a goal in mind? Haven't got a main character in mind? Here's an exercise to try:
Write down the names of every one of your characters. Yes, all of them...
Go through each character and write down the one thing that could happen to them that would change their lives forever. I'm talking about major life change:
What would destroy them?
What would have them raging at the heavens?
Or, on a brighter note: what do they treasure the most in their world?
What do they have to lose?
Go through your list now and find the character with the most to lose. This should probably be your main character. If you've already got a main character in mind, see what you wrote down next to their name. Imagine that this 'event' actually happens. What would they do?
That's your story: what your main character will do once they lose the thing they treasure most.
For an example, my work-in-progress begins with the relationship of Inoperable Squirrel and his Uncle Thor. Thor means everything to I.S. When Thor disappears, I.S. sets out to find him. This is his major goal: find his uncle.
For an unfocused writer, putting a goal as #1 may bring inspiration to your narrative.
Here's another quick example:
Cindy is a princess set to be married to her true love Sebastian. Sebastian has promised to take her away from the kingdom of her evil uncle Maurice. But King Maurice hires a dragon to kidnap Sebastian. Cindy sets out to find her true love, knowing that death awaits her if she stays in her uncle's kingdom.
The evil king sends his evil minions after her, but she is saved at the last moment by a peasant named Jake. Jake agrees to take her across the ruins of the kingdom to find the lair of the dragon. All the way, they are dogged by Maurice's minions, and faced with the trials of passing through a cursed land.
When they finally reach the dragon's lair, Sebastian reveals that he made a bargain with the dragon to replace himself with Jake. Happiness! But Cindy realizes that she has fallen in love with Jake. Who will she choose? What will she do?
I'll save you the happy ending, folks (and it would have been good), but see all the trouble Cindy gets into by having the one goal of saving Sebastian? This gives rise to all sorts of drama! See how much fun you can have?
For some extra examples in the real world:
Books: In The Shining, all Jack Torrance wants to do is finish his novel (the goal), so he takes a job as caretaker for an aging hotel, hoping to find peace and inspiration. Too bad the hotel is just a tad haunted...
Movies: In the recent movie Juno, Juno finds out she's pregnant and decides to keep the baby. Her goal is to find appropriate adoptive parents for it.
TV: In Lost, survivors of Flight Oceanic 815 land on a myserious desert island. Now all they want to do is find a way to get off of it...
And for real-life drama, just take a look at Henry the 8th. All he wanted to do was marry Anne Boleyn and divorce his wife Katherine of Aragon. In order to achieve his goal, he created the Church of England.
Try for some motivation, folks. See what happens.