How long should you leave ribs on the grill?

You will know, but in case you don't:

Make sure the fire stays low (or out). Just let the heat from the coals cook the meat, slowly. Pork is one meat that must cook thoroughly or you risk eating live bacteria. Here is how to tell, cheat. You will see the meat darken and look like it is done in about 30-40 min (depending on the slab size). Take your knife, cut a slice down one of the rib-bones and make sure there is no blood or the meat is not red. Do this in the thickest part. If it is Red still, make a few cuts in the thick parts of the meat so that the heat can cook in there. If the meat is white, tender and yummy...take your slab off OR do like I do, lightly layer some homemade BBQ sauce on it at that time to coat the outside. Let that stay on for about 5-10 minutes (you will see the meat really darken and the sauce dissappear into the meat while cooking). Take it off then, because she's ready.

Have another sauce with cooked onions etc...ready for those that must drown the meat in sauce. For those that don't, you have just given their taste buds a small slice of heaven also.