In order to get moving on the product, I will do a rough ranking to determine which areas are most important per the three questions above. This is what Getting Real calls finding the epicenter.
A good way to think about this is: which parts of the app will teach me the most about the problem by working on them? This is the exact opposite of what programmers often do when they build the “knowns” first, like user-authentication, before they dig into the hairier domain-specific features.
The end result of this ranking is something like a heat map that reflects my assumptions about where the value is in the product.