So I'm wondering what strategies there are for determining the class of a neighborhood (i.e. labeling certain neighborhoods as A-class, B-class, C-class, warzone, etc..)?

For starters, you'd want to consider the location and general age and price of properties in the neighborhood, ratings of nearby schools, amount of crime, vacancy (homeownership and rental), plus grocery stores and shopping centers nearby.

A lot of this info can be found online (e.g. school ratings, crime maps, property age, grocery stores and shopping centers), while some of it can be determined by driving the neighborhood and talking to folks that live in the neighborhood.

Asking police about a neighborhood might give you some objective info on crime, talking to property managers might give you info on vacancy and rent prices, and talking to a real estate agent might give you info on property age and price. 

Are the other professionals (or strategies) that could provide insight into classifying a neighborhood?