Step 3: Neck relief and curvature
One way to measure the amount of relief is to hold down the first and last frets, and to measure the height from the 7th fret. A good/fair amount of height should be around .1 mm to .4 mm.
The second way [the lazy mans way], which is the way I usually do it has basically the same idea as the first way but you measure from the 12th fret., only you don't measure. instead [while holding down the first and last frets] use the thumb of the hand holding down the last fret and tap the string over the twelfth fret. there should be a relatively small gap between the two. If the string touches the fret then the curvature is too straight. Little something i learned from a youtube video sometime ago.