How to measure pinion angle?

I have done a lot of reading on how to measure for ponion angles and have not found a link that does not confuse me. Can anyone help me out I need to measure my rear pinion angle and adjust for bad vibrations

Try this one it has a pretty good write up.

http://www.4crawler.com/4x4/CheapTricks/Driveline-101.shtml#Double-Cardan-Measurements

Also try reading the tec info on Tom Woods drive shaft website:
http://www.4xshaft.com/
Pretty good straightforward explanations there.

spin the yoke until it has the saddles for the ujoint facing vertically, then lay your angle gauge, or angle finder across the yoke like the ujoint would sit in it. compare that to the angle of your driveshaft (assuming you have an sye) or to your output shaft (assuming that it still has a slip yoke type output shaft)