To expand on Arcs' comments:
After applying smoke (and heat) to the ribs, you can wrap them in foil or put them in a disposable foil pan covered with foil, with a little liquid to finish the heating process. By covering the ribs and adding a little liquid (apple juice, jack daniels, wild turkey, the list can go on and on), while they continue to cook, the ribs won't dry out and they will also get real tender.
Caution, heating the ribs wrapped up can cause the meat to fall off the bone. So if you don't want the meat to fall off the bone you will want to unwrap them a little early. This will also give you the opportunity to add some bbq sauce and glaze them on the grill.