This is what I did yesterday for 7+ pounds (3 slabs) of baby back ribs:
Place the ribs in a container and pour orange juice on them (they don't need to be submerged or anything like that) and let them soak for 30 - 45 minutes in the refrigerator. This will add some sweetness to the ribs and make them a little juicier.
Place them on cookie sheets and apply a sweet rub. I used one from a store (Sam's Club?) that was a Saint Louis style and that had a decent list of ingredients including brown sugar. Preheat the oven to 250 degrees, cover the ribs with foil and bake for 60 minutes.
Take them out, turn them over, and sprinkle the rub on the other side. Cover again with foil and bake for another 45 minutes. Do this process again for a total cooking time of about 2.5 hours.
Remove from oven and let stand for 15 - 30 minutes. Then place in a fridge for 2 - 3 hours. Fire up the grill (fairly high heat to start) and place the ribs meaty side down, then reduce the heat to a fairly low setting. Turn occassionally for the next 20 - 30 minutes to avoid burning or over cooking any of the sides.
Then place the ribs meaty side up and apply a BBQ sauce (I used one called "Sweet Baby Ray's"). grill the ribs for another 15 - 25 minutes, flipping them and adding sauce every so often. Should get 2 or 3 coats on both sides of the ribs before pulling them from the grill.
These were the best ribs I've cooked to date. Very juicy with an excellent flavor.