Start at the basics of pepper with a little salt and work from there. The rub that I use on all pork (and mix 50/50 with black pepper on beef) contains:
Black Pepper
White Pepper (very small amount)
Spanish Paprika
Hungarian Paprika
Ground Chipotle (small amount)
Chili Powder
Cayenne
Tony's Creole Seasoning (I use this rather than a season salt)
Some folks like to add ground celery, onion powder, and/or garlic powder. I dont.