Take it from a mountaineer with plenty of backcountry travel experience:
LEARN CLOTHING SYSTEMS.
Period. The other folks on here are not wrong: Footwear is very important, but frankly, ALL your clothing is important. You're creating a micro climate to carry with you that is critical in *keeping you alive*.
A good start primer would be "The Art of Not Suffering" by Andy Kirkpatrick, found here:
http://www.psychovertical.com/?theartofnotsuffering
It's geared towards climbers, obv, but the lessons can be carried into pretty much any outdoor activity.
