Originally Posted by: Razbo
Question: How can you say it is half the length of the string if it is not intonated? [/QUOTE]

Well I tune all the open strings to pitch, then tune the 12th harmonic to pitch. When they match, I know it is half the length.

[QUOTE=Razbo]I didn't come up with this all by myself, I confess. Most tutorials I've seen do not suggest using harmonics. The only place I ever see that is on Forums. ...You know, those places where the sources are dubious and everyone is an expert? ;)

Here is a good one
http://www.projectguitar.com/tut/intonate.htm

What if you run into a situation where you tune the open string and the 12th fret to the same pitch....but then your 12th harmonic is off (sharp/flat)?

This is one site I was going by:
http://www.icepoint.com/guitar/Setting%20up%20your%20electric%20guitar/