This is the recipe I normally use for a rub.

Rub Ingredients:

• 1 tablespoon mild paprika
• 2 teaspoons light brown sugar
• 1 1/2 teaspoons hot paprika
• 1/2 teaspoon celery salt
• 1/2 teaspoon garlic salt
• 1/2 teaspoon dry mustard
• 1/2 teaspoon freshly ground black pepper
• 1/2 teaspoon onion powder
• 1/4 teaspoon salt

For the meat:

• Boston butt bone-in pork shoulder roast. If Boston cut is not available, Picnic Shoulder does just as well. They're both from the same side, one is the higher cut on the loin and the other is the lower cut.
  

Combine all the rub ingredients in a glass bowl, mixing well until evenly blended.

Cooking Pork Shoulder by Tom:
I rub a shoulder down generously on all sides, then cover it with plastic wrap and put it in the refrigerator for 3 or more hours. Set the oven to 225 degrees, remove the plastic wrap and place the shoulder fat side up into a glass pan with at least 2 or 3 inch high sides . Fat side has to be up so the fat melts and bastes the meat. Score the fat with a sharp knife down to the meat using a checkerboard pattern. Cover the shoulder with aluminum foil and cook for 8 hours. A good way to do this is to put it in the oven the night before around 11 PM. It will be finished at 7 AM.