The day before the meal, trim all of the excess fat that is thicker than 1/4 in., rub shoulder with olive oil liberally, and then apply you favorite BBQ dry rub, for pork you are better off with "sweeter" Kansas City or Memphis style rubs in my humble opinion. Depending on your smoker, the rest is all variable. The meat will only absorb the smoke for the first few hours or so, so keeping the smoker smoking after that is not necessary. The most important thing is a stable temp for the long burn, between 225-250 deg. It is very hard to over cook a pork shoulder if you keep the temps steady and low. Spraying or basting with a 50/50 mix of olive oil and apple juice is fine if you only do it once or twice over 8-10 hrs, "cuz if your lookin, your not cookin", and your temps will suffer...Happy smokin'!