Jim Langley gives the plumb line forward/aft methodology:
http://www.jimlangley.net/crank/bicycleseats.html

Peter White gives what I'm calling the "unique personal body mechanics and how do you want to ride" methodology.
http://www.peterwhitecycles.com/fitting.htm

I set up Magpie (my hill climbing bike) with based on the plumb line because that's how I've always done it, but I keep finding that she wants the saddle forward. I moved the saddle forward because I thought I was too stretched out. Finally put on a shorter stem and moved the saddle back because "this is the way you're supposed to do it." I've matched all the numbers on my other road bikes. BAD! I still have to experiment but it seems like the bike rides/climbs better with the saddle farther forward than the plumb line method would set the saddle.

So, I'm taking the Peter White article home to 'speriment.