its kind of trial and error and alot depends on what final product you are after... first the method, 3-2-1 or whatever, the first number is basically your smoke number, how long it sets in smoke and builds bark. the middle is the braising number where you have in foil and the meat is braised in the liquid you have provided. this generally infuses the meat with the mop and it the prerequisite to your fall off the bone ribs. the third number is sorta a hardening time, this period resets the bark that has been softend by the braise and lets you get to texture you prefer.
so by adjusting these times you can control certain factors to get the ribs you are looking for.and everyone has there own personal preference on how they like them. some like em falling of the bone tender while others prefer to have a little chew(my favorite) to come off the bone. either way the bone should come clean.