I agree that this is an excellent thread. However, one of Mark's suggestions on learning chords is "If it hurts your hand to make the chord, practice more often." I would suggest being careful about this one. Very often, pain is a sign that something is wrong, and pushing through the pain is the last thing you should do. I've had this experience myself, a few years ago, when I started to develop carpal tunnel syndrome. The solution was NOT to "practice more often" -- that would only have made it worse. The solution was to analyze why my playing was causing me so much pain, and find a different approach (in my case, changing my hand positions), so that the pain would go away.
Just a word of caution about one point in Mark's otherwise excellent advice.