Combine all ingredients in a small bowl (except the ribs) and set aside.
Using a paper towel, pat the ribs dry. Remove the thin membrane attached to the underside of the ribs. You can do this by sliding the tip of a knife between the membrane and bone and pulling the membrane. Pull the membrane all the way to the other end, using the knife to free it if it catches anywhere.
Cut the racks in half and place two halves on a sheet of foil wide enough to wrap up the two halves completely. Rub a quarter of the spice mixture into each half rack of ribs. Wrap the ribs up in their foil so that two halves are side by side in each packet. Make sure the packets are completely enclosed.
At this point you can grill right away, but for better flavor let them sit in the fridge for up to a day.
If you're cooking in the oven, take the ribs out of the fridge while the oven preheats to 325F. It's best if the ribs sit on the counter for at least 20 minutes before cooking. Cook the ribs in their foil packets on a baking sheet for about 2 hours.
If you're grilling, spray the grill tines with cooking oil and heat the grill to between 350 - 450 F.
Remove the ribs from the foil and place them meaty side up on the grill. Brush them with your favorite barbecue sauce and close the grill. After 5 minutes, flip and brush them with sauce again. Continue to baste and flip every 5 minutes until the sauce has thickened to a nice crust and the ribs are heated through, usually about 20 minutes.
Transfer the ribs to a cutting board and cut the rack between the bones. Serve with the rest of the sauce.