Neighborhood classification system?

What “neighborhood classification” system do you guys utilize?

I have heard of one from David Lindahl (sp?) that uses a A - D scale to kind of generalize about the neighborhood and says that he tries to stick to “B & C” types of neighborhoods.

I have also heard of another system that uses 1 - 5 to rate the neighborhoods.

What ones are you guys using?

Details please!

I use the “Get into the car and drive around and look at every street within a couple of blocks” classification system.