I have been smoking a lot this summer and a new trick I have been doing is putting a smoke pack right in the BBQ with the ribs... Always indirect heat and I turn the BBQ as slow as possible and let it ride. The cooking time is about three hours at 180 degrees - I have just used maple this year, and everyone seems to enjoy; never leftovers!!!
To make smoke pack, get small pieces of maple, no bark, and wet them and wrap it up in aluminum foil put it right on the part of BBQ with heat/flame and let it smoke away...