And its annoying to see people do it the wrong way or pathetically. You see people do heavy weights but either dodgy or really quickly, people should learn its not about trying to lift heavy weights, I really take my time when I am doing reps I take them rather slowly; its recommended that you bring them up without too much speed and bring them down twice as slow, as when you are bringing the weights down it is at least as important as pulling them up.
Something interesting I heard recently essential for muscle growth is failure at the very end. In the past I didnt put much into the last rep you know you cant pull up after however many but failure is the most important part of the whole part for muscle growth. I have been told that when you push it until you have absolutely nothing left, even if you fail to finish the rep you muscles essentially panic when put under that much stress and that is the part that really forces them to grow. When I first pushed to the point that I had nothing left at all I could feel the difference.