ORIGINAL: vertical grimmace
It is important to realize that the incidence needs to be measured through the centerline of the airfoil and not simply by using a ruler or straight edge on the bottom of the wing. A common error. That is why I like a commercial incidence meter as they center themselves properly with the airfoil.
Realizing the importance of that, I made a jig that centers the platform, on which the angle meter rests, on the leading and trailing edge centers. A simple V shape on the beam ends between the edges insures this. You do not need the expensive commercial meter unless you are incapable of constructing this simple jig that I made out of wooden paint sticks free from the big box hardware stores. Or unless you have excess money to spend.