While you are prepping the ribs, start preheating your pellet smoker at 225F. It is important to follow the instructions and start-up procedure of your brand of pellet smoker.
Ribs usually come with a thin layer of tough skin on the underside of the rack. This is called the silver skin and it needs to be removed so the seasonings can penetrate the meat. See the video in the post above for insutructions on how to best remove.
Lay the ribs on a sheet tray and add about 2-3 tablespoons of rib rub per side. You don't want to completely coat them...leave some meat peaking through.
Once the smoker is pre-heated, you can put the rack (or 2 racks) directly on the grates and let them smoke. Leave them alone for at least 4 hours. The less you open the grill, the shorter your cook time will be. You do want to keep an eye on the smoker temperature and make sure it stays where you set it.
A rack of baby back ribs will take 4 to 5 hours to cook and spare ribs will take 6 to 7 hours.
Towards the end of the cook time, pick up the ribs with tongs and if the bark breaks and the ribs almost split in half, they are done. If not, keep on smoking.
Add BBQ sauce (optional): When the ribs are ready to come off of the smoker (they passed the bend test), you can coat them with a thin layer of your favorite BBQ sauce. Leave them on the smoker at 225F for 30 more minutes so the sauce can caramelize.