i've searched the posts here and read many sources on how to get a pork shoulder to pull. I've seen another guy's comments (he is the author of another BBQ book) which said that pork will not pull unless you smoke it at at least 275 deg. He had "scientific info" to back this claim up, but my experience did not agree with this. in the past i've always cooked the pork in my weber grill (always following the directions in Steven's books) and never got it to pull.
I finally found a full day that i didn't have to do anything except watch football, and smoked a 4 1/2 pound shoulder in my vertical smoker at about 210-220 for 13 hours, wrapping it in foil the last 3 hours. It just fell apart when i started to try to pull it. It was the most tender, most pullable pork i've ever made.
So "low & slow" is definitely the way to go (hey, i'm a poet).