Tips?
First one would be to delete the word "...but..." from your dictionary. Pretend it never existed. Makes arguments over your comments less likely. "I know you want extra legroom but there aren't any spare seats" compared to "I know you want extra legroom and I'd let you have one had there been any spare seats". It probably doesn't work so well on a computer screen but in real life it seems to be helpful. (Wife is a Pshrink/union negaotiator and thus a highly experienced and very devious bitch when it comes to arguing)
Second would be to know the difference between open hand gestures and closed hand gestures. Seems to go back to caveman times when a closed fist represented a sharp rock or a pointed stick that the caveman was going to use on you. If he waved an open hand (standard worldwide "hello" gesture) it meant he wasn't threatening you. A balled angry fist or a pointing finger in the face is a visual representation of the sharp rock and pointed stick. If you can keep your palms facing the miserable b45tard then it seems to subconsciously say that you aren't threatening them and, lets face it, they are often angry because they are going to be propelled in a small alloy tube at high speed/altitude without any control over their own destiny and will react accordingly. As mentioned above somewhere, treat them a bit like frightened children who are lashing out in frustration. Failing that, a kick in the b0110cks works quite well.