You want to know which families are cuttable and which are not. Revit 2011 help gives the answer:
Cuttable families (link):
Curtain Wall Panels
Non-cuttable families (link):
What is a cuttable family?
If a family is cuttable, the family displays as cut when the cut plane of a view intersects that family in all types of views. From Revit 2011 help.
How to make your own family cuttable?