References, references, references. And references. Hire an independant inspector or supervise the job yourself if you are knowledgeable enough.
While I was laid-off a few years ago, I designed and built a 1000 square foot two story extension on my house including a livingroom, den, and master suite. I got permits, hired all the trades myself and supervised, supervised, supervised. I did all the interior work myself. No matter what, there will be road blocks and forks in the road. YOU, the owner, or a representative, needs to be there to make decisions and assure quality. Trust yourself, and trust references a little.