Execellent FAQ thread. May I suggest a couple things? A few pictures here and there would make your FAQ thread very "lively".
#1. What’s the difference between spruce and cedar tops?
A pic of spruce and cedar would be useful for newcomers to the CG world.
#2. How does humidity affect my guitar?
In Jose Oribe's Book there is a nice picture showing the soundboard width at different Relative Humidity.
A picture showing the effect of RH on a piece of soundboard would be very educational for all of us.
#4. What is the correct action for a classical guitar?
I think a few of your own pictures like what Kenny Hill did would clear all questions re how to measure actions (such as where to measure it, and measure from TOP of fret to BOTTOM of string). Or maybe a link to Kenny Hill's website is sufficient?
http://www.hillguitar.com/scripts/frame ... setup.html
#20. How should I change the strings on my guitar?
Another useful thread (in addition to the link you already provided) is Bridge Tieblock Gallery:
#21. Care for the instrument and Damage prevention
Things such as how to clean it (? damp cloth), how to hold it (? by the neck etc.). How to pass it to another player w/o damage etc. etc.
Also after playing, place the instrument back to the case and CLOSE the lid and LATCH it.
One never knows someone decides to move the UNLATCHED guitar to another place and it will fall out of the case if unlatched (I learned this from Oribe's book).
Likewise, It is not adviseable to put the guitar back in the case and leave the lid open.
Also do not leave the guitar on the couch or sofa, someone may sit on it (the guitar will screammmm!) or a pet (cat or dog) jumps on it (the guitar will cry!) etc.
Anyway, just my 2 cents.
Execellent thread by the way!