For a symmetrical airfoil type plane, draw a line right through the center of the wing for your reference line. For a totally flat bottomed wing (unusual), the flat bottom is the line to use. For a semisymetrical (that's an oxymoron...) wing draw the line from the center of the rounded leading through the trailing edge. Set these lines at 0 degrees with the stab for starters.

I'm open for corrections MinnFlyer; also thanks for the description of using the GP incidence meter. I need one!

Ernie