Thanks for the comments.
In the book, I recommend building a healthy team as the first step. If you already have this, great! It's a lot easier to sit down and figure out what your biggest problem is.
If you can't really do that as a team, at least you've identified your biggest problem.
That's where I'd start. Chances are, everyone can identify something that you could do better. Trace those back to the source and you have a starting point.