Understand what a Scope of Loss is. In short, it's a document that describes in detail the house that you'll be replacing or repairing in the event of a disaster.
See a sample (a PDF file) of a typical Scope of Loss at CareHelp's web site. Run by Oakland Fire survivor George Kehrer, CareHelp is a non-profit organization that offers free advice to wildfire survivors, mostly how to best deal with insurance companies.
To conduct your own Scope of Loss appraisal, you'll first need to interview prospective architects and contractors. Make sure that they've had some prior experience with insurance claims. According to CareHelp, "Even better, find one who has defended his estimate in court in the homeowner's favor."
In our case, we interviewed an architect first, a friend of a friend, only because I was once an architecture student and had learned to have a deep respect for the profession. Luckily we liked him immediately and he, in turn, recommended a contractor friend that he trusted. So, we used both an architect and a contractor to compile our Scope of Loss.