Orthographic representation is obtained by means of parallel orthogonal projections resulting in flat
2D views systematically positioned relative to each other.
  
The most informative view of the object is normally chosen as View A.
This, for example, would be the objects normal working, viewing or mounting position.
 
Positioning of other views relative to View A will depend on the projection method chosen (1st or 3rd angle)

Important:
  
Avoid unnecessary repetition of detail.
Limit the number of views to the minimum necessary to fully represent the object without ambiguity.