That, which

Recently I realized a rule of thumb to rely on in regard to using "that" or "which."

My pod mate (new age cubicles), Marshall, said:
The phrase following "that" effectively becomes an adjective and is necessary information to define the object.
The phrase following "which" is information not necessary to the object
It also should be preceded by a comma.

So...
The wicked witch lives in a castle that is haunted.
The wicked witch lives in a castle, which is in the east.