I wanted to take a character and transform him from Mr. Chips into Scarface.
Having a rock solid idea of how it all should end is counterproductive. If you're too rigid you may miss wonderful opportunities for storytelling.
Don't make any of your plotting decisions out of fear or desperation. Keep the story and the characters simple.
We love the idea that all actions have consequences.
Having certain limits on an ability to tell a story makes us work harder.