The main thing I've learned is: A surprising percentage of the time, the cache is in the last place I look. (before you say "duh", admit you've looked in holes, etcetera and didn't see the cache that is there.
Another thing: Geocachers don't have as much a sense of humor as you might hope. I learned this after hiding a micro with a 6 inch thread attached to a fake spider. (yeah, it's funny if it happens to someone else...)
and another: An hour long conference lunch break is a half hour too short to grab that cache you've been hoping to get to.