I have about a gazillon of chapter one's lying around. And just as many story ideas.
I've just recently discovered my mistake. While I had the characters and the story arc planned, I often neglected to flesh out the rest of the world in sufficient detail.
My solution, which I kinda stumbled upon, was PlayByPost roleplaying in online forums. I'm currently DMing a game and I quickly found that I had to work a lot more on the details of the world than in my regular fiction. With that and the constant feedback from my players I was able to write roughly 25000 words in one month. I almost fell off my chair when I did the word-count. (I'm SO signing up for NaNoWriMo this year.)
So to stay on topic; what I've found to work best is to select a few good critiquers on web forums and let them tear your work to shreds. Friends and family often have a misguided sense of loyalty, and tend to prioritise your feelings over giving you actionable feedback.