whynotfab
+1y
The picture is just a reference, not an exact angle. If you are referring to a single driveshaft, find the angle of the tranny output, and set the pinion angle to the Equal Opposite Angle. So for example, if the tranny points DOWN 2 Degrees, Set the pinion pointing UP 2 degrees. Do all of this at ride height of course.
As for the tool, most people use the $10 angle finders from Lowes/Home Depot/Ace.
If I left anything out im sure others will help out and add to it. 2 Piece driveshafts are a little more confusing. Hope I helped some.. good luck.