If desired, soak the pork butt in a brine solution for at least 4 hours or overnight. There's a recipe for a brine on this site titled 'Basic Brine for Smoking Meat'. You should do this covered and in the refrigerator.
Preheat an outdoor smoker for 200 to 225 degrees F (95 to 110 degrees C).
In a small bowl, combine the brown sugar, chili powder and any additional seasonings to your taste. Apply this liberally to the meat and rub it in with your fingers. Place a roasting rack in a drip pan and lay the meat on the rack.
Smoke at 200 to 225 degrees F (95 to 110 degrees C) for 6 to 18 hours, or until internal pork temperature reaches 145 degrees F (63 degrees C).