I believe it is the proper amount of heat to the right point of causing the skin to break down, that and make sure there isn't a lot of fat underneath the skin.
I noticed some will cook skin side down and others will scrape some of the fat off from under the skin before smoking.
They did theys in a pan with some broth and smoked for a hour or so to break down the skin then it was back into the smoker for the rest of the smoke. It was on that show on food network last night. I think thats the team that is ahead of Myron in points for the KCBS. I personaly don't worry about the bite thou because the first thing I eat. I just pull off the skin and eat it. then it's back to the bird.
I have seen several methods for this. One is to pre-crisp the skin on a hot Weber grill then smoke it. Or (the one I have used) sauce the chicken 1x about an hour before you pull it. I did this last weekend and the skin turned out very edible. It wasn't super tender like competition chicken, but you could either bite through it or cut it with a fork just fine.
I have always crisp'd up on the grill after smokeing, and sauced rite before goung into the box. I have also painted on some vingar then rubbed and set for an hour in the cooler, than smoked, that will get it also.
I did have some chicken one time (and I never eat the skin) that had such a great fall apart, melt in your mouth skin that was so good I couldn't believe it but of course I have no clue what I did that time because I didn't pay much attention to the prep part of it and just did whatever then smoked...
*lesson learned (sort of), always keep track of your smokes and recipes and note any changes you make.