High quality pencils, compass (engineering style), a well oiled CRP computer with the screws tightened (but not too firmly), a long ruler not just a plotter but one that will take you further a single pencil line, etc.
But of course all that is academic because the essential thing is knowledge of the subject matter. A good book on the subject is "Ground Studies for Pilots: General Navigation" by R. B. Underdown.
Hope that helps
