I remember, many years back, when I learned to backpack. Before reading The Complete Walker (the original), I relied mostly on what I learned by asking others (mostly Scout leaders, since my son and I were both learning-by-doing with his Scout troop.) Much of what They told me turned out to be wrong. (I don't think They intended to mislead me; they just gave me maxims instead of teaching me the logic behind their technique. I later learned that everything They knew had been passed down as Rules by Others who taught Them.)

Some of these included:
Sleep naked, you'll be warmer.
Always carry 2 liters of water; doesn't matter where the next source is.
Always build a campfire (it's upholding the 'Murican pineer heritage), even if you have to build a new fire ring.

Anyone else have some favorite things They taught you?