[1]  define a range of levels to meet planning and operational needs – more than 5 levels may be confusing, fewer than 3 may not differentiate sufficiently, [3]  invite participation by experts with a variety of different knowledge and skills applicable to the hazard type, [4]  describe the purpose of the process and provide an overview of what you know about the hazard, and [5]  develop consensus through discussion and balancing of this hazard against the others you face.

The danger is that a large number of hazards will be seen as being highly hazardous.  As a result there may be insufficient differentiation of the hazards to support planning and resource prioritization.  This means there must be substantial agreement on the rating range for each event.