I'm a huge fan of spending time building characters before beginning the plot.
1. Label your main characters' greatest fears and desires.
2. Write a narrative around the root of each of those fears and desires. What was the moment that created the emotional scar, or the euphoria?
3. Repeat this process for ten fears and desires.
The goal of this exercise is to bring your characters to life. Think about how you act on a regular basis. We are faced with millions of choices every day and each choice comes up against an unconscious fear vs. desire. Even simple thoughts like what to have for dinner. Desire for flavor vs fear of gaining weight. Choices like whether or not to be honest with our spouse about our sexual desire for fear of being romantically rejected. If you can build the source of each of these fears and desires for multiple characters and then stick them in a room together with goals they want to achieve, they'll play off each other like ping pongs.
The idea here is that if you develop them well enough, they'll have their own agendas and you'll just be the conduit. If you're having to "think" too much, then your characters are not alive and chances are good that they will all sound a lot like YOU, not themselves.
Once I have my character bibles down, I do a skeletal plot outline; only one sentence per scene. (Because the character bibles are done, the characters inform the outline.) Then I move into an in depth outline, similar to what screenwriters call a treatment. One paragraph per scene. This gives me time to really dig into the plot and I make the majority of my big changes here which saves SO MUCH time when I move into writing chapters.
Then I begin with chapter one, knowing it will be the chapter that will be rewritten the most. I don't start with exposition mind you; I begin by dropping the characters into the middle of conflict. "John felt for the wedding ring in his pocket as Mandy cornered him in the alleyway that night. She had already killed three people in the last hour and John was the last one blocking her path to freedom." CONFLICT where both the protagonist and the antagonist have a reason to fight for their life, figuratively or literally.
I use chapter to create the style and the rhythm that I'm looking for in this particular piece. Then I move chapter by chapter, attempting to stick to the outline, but not being afraid to stray if the characters tell me they have agendas that they have to explore.
I hope this helps you! Oh yeah...and "sit your ass in the chair and do your damned job!" When I get stuck I look over at that sign I have posted on the wall. It was something a business coach once told me and I've never forgotten it.