The most effective way I've been corrected was when I was fading in a paceline on a team ride. I tried to pull through, but the guy coming off accelerated a bit, we were headed up a rise, and I just couldn't get past him to move over. Local pro rides up beside me, puts a hand on my shoulder, and says simply "Don't pull through unless you are sure you can do it, or you disrupt the line." Lesson learned.