Have a good set of construction documents/plans. This will help minimize change orders and unexpected costs.

The time to ask a million questions is during the planning stages. Understand the plans - REALLY understand them. Have all your stuff selected and have photos, names, where selected, measurements, name of material, colors - everything before the build starts. Then concentrate on the build once it starts. Don't just say I want Dove White walls. Say I want BM Dove White walls in X grade of paint and flat finish. Don't leave anyone to guess at what you want. Don't assume anything - miscommunication happens and people can't read each other's minds. COMMUNICATE, COMMUNICATE AND THEN COMMUNICATE SOME MORE.

I'm finishing an attic as I type. Lack of communication between everyone has already been a consideration. Get a three ring binder, have pictures of what you want, detailed plans, notes of conversations you have. Details and more details. Do your homework. Don't just say insulation- say what kind. Make sure the contractor and the guy running the site- if they are two different people- are on the same page. And yes, supervise. I went up today to find a wall going up today where it is suppose to be a pony wall. Lack of communication yesterday had the HVAC guy now running his stuff into the rafters instead of along a wall. And I built this house. So I've been there and done that. You would think I would be ahead of these issues.

Keep your emotions out of it - it's a business transaction between you, the bank, the builder and everyone in between. Don't pay for anything until it's done and done right. Do not go outside of the scope of the contract unless it's written down and everyone signs off on it. Oh, make sure that contract is detailed and reviewed by a lawyer.

Keep track of costs and of time spent on the project. Make sure that you have all the details worked out and that you aren't making changes at the last minute. Good luck!