I've been smoking pork butts for 8 years now. I've tweaked my method of prep, smoking, and my rub over the years to reach what I consider the best pulled pork I have ever eaten.
I've fed my church(even turned a vegan into a carnivore for a day!), large family gatherings as well as a precinct of Portland Police Bureau with the help of my brother in law 
The Prep
To start use a pork shoulder blade roast(Boston Butt), rinse, pat dry, and poke three holes about 1.5 inches deep(I make an x or cross). Spread using finger, and fill with rock sea salt into each hole. Then lightly sprinkle the whole outside of the roast with sea salt.
The Rub
1 cup light brown sugar
2 tablespoons of Lawry's Smoked Chili and Garlic Blend(Find on Amazon.com)
2 tablespoons garlic powder
2 tablespoons onion powder
2 tablespoons chili powder
1 tablespoon paprika
2 teaspoons ground cinnamon
1 teaspoon ground cumin
1 teaspoon crushed red pepper
1 teaspoon cayenne pepper
The Smoking
I use a applewood chunks over charcoal. You want temperature of the smoker at around 225 degrees Fahrenheit. + or - a few degrees.
After about 3 hours, begin spritzing with 2/3rds apple juice 1/3rd Apple cider vinegar mixture, about every two hours. Or when the shoulders look dry.
Time
Smoke until the shoulder's temp is at 160 degrees, then wrap with foil, and return to the smoker until it reaches 190 to 200 degrees. For this demo I did 2 pork shoulders 8 pounds each. I smoked from 8am to 6 pm, wrapped and left on the smoker till 10 pm.
And so here it is, my pork shoulder with crispy, sweet, spicy, smoky bark and all that tender, juicy, applewood smoked flavored pulled pork.
Don't worry about smoking too much meat. Bag it, or vacuum seal it and store in freezer. Defrost, and reheat in a frying pan, or reheat in a slow cooker with a quarter or half cup of apple juice.
Thank you, and get to Smokin' and Steemin'!!!