its a method ..
3 hours on the smoker 225 ish
2 hours wrapped in foil 225ish
1 hour out of foil 225ish ..
best used for spares ..
more like 2-2-1 for baby backs ..
The range you want to keep the ribs is 200-250. 225 is pretty ideal. If it is hotter then cut down the cooking times, lower increase them.
I don't believe that meat takes on any more smoke flavor after a couple of hours so I only smoke for 2 hours. Smoke wood is too damn expensive to waste for that third hour.
When I do ribs with the 3-2-1 method I apply a liberal rub at the beginning of the process but have plenty of extra rub. When it is time to foil I slather the ribs in honey or syrup. Sounds nuts, but trust me. Then add more rub. Into the foil for a couple hours. When the ribs come out of the foil the rub will be mealy and gritty. Back into the cooking chamber for another hour or so to firm up that rub into a nice bark.
If you don't want the extra bark just slather in honey or syrup and foil.
Here is a pic of some baby back, bone side down getting slathered:
If you plan on saucing your ribs with BBQ sauce then do not add any more rub.
My dad has poured wine or beer in with the ribs in the foil which is pretty awesome too...