4. Don't blame everything on the contractor
You say the guy is a blundering idiot? Well, who hired him?
A project gone south is like a marriage gone bad: you should consider the possibility that it's at least partly your fault. Failing number one: lack of communication. Some people expect contractors to just know. Take it from me, they don't. You have to clearly explain what you want at the outset, check on progress periodically, and let the appropriate parties know when things go off the rails.
That brings us to failing number two: unrealistic expectations. It's a construction project; things are going to go wrong. The proper response is not to rant and rave and decide the contractor is incompetent, but to calmly discuss the problem and agree on how to fix it. That done, if things don't get fixed, a little ranting and raving may be called for.
My point is that you need to be reasonable, and look at things once in a while from the other guy's point of view.