Mix spices: Combine paprika, brown sugar, garlic powder, onion powder, pepper, salt and cayenne in a bowl.
Prep pork: Pat pork shoulder dry and rub spice mix all over it.
Layer crockpot: Place sliced onions on bottom, then add seasoned pork on top.
Add liquid: Mix BBQ sauce, apple cider vinegar, broth, Worcestershire and mustard; pour over pork.
Cook: Set to LOW for 8-10 hours (or HIGH for 4-5 hours). No peeking!
Shred: Remove pork, shred with two forks, discard any big fat pieces.
Finish: Return shredded pork to crockpot juices for 10-15 minutes to soak up flavor.
Serve: On buns, in tacos, over rice - however your family likes it!