Don't forget Kansas City!!!
True barbeque has several main components:
First and foremost is the use of indirect, low heat to slowly cook the meat. Known as smoking, it imparts that predictable flavor and smell. Using different types of wood (apple, maple, mesquite, hickory) can change the taste of the final product. The use of a steam bath keeps the meat moist while the fat is reduced. The contents of the steam bath are another area in which you can change the flavor (my dad uses orange juice, apple juice, and beer for the liquid in his steam bath, the rest is secret

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The meat can be marinated, but traditionally, the use of a dry rub is key. One of the cook's great secrets can be the recipe used. The rub is simply a mixture of various spices that is rubbed on the outside of the meat. The spices are chosen for complementing the sauce and making sure the meat has that taste through and through.
Sauce is where many regions vary. In Kansas City, the base of the sauces is tomatos...not ketchup, though that can be used but you have to make up for the sweetness. In the South, the base is more often vinegar. KC sauces tend to be thicker and sweeter, IMHO they are also more balanced between sweet, smokey, savory, and spicy. Southern sauces tend to be thinner, and have a sourer taste due to the vingar obviously.
Pork is more traditional, especially when it comes to ribs. Beef ribs suck major balls unless you are willing to cook them for like a day and a half in order to make them tender. The greater fat content for pigs helps make them more tender.
Things that barbeque is not: Grilling pork butt steaks and putting barbeque sauce on them. Actually any grilling is not true barbeque.
Also, IMO boiling your ribs is an unforgiveable sin. Take the time to set up a smoker correctly and you'll get more flavor, and tenderer meat. The boiling also in my experience has negative effects on bone consistency, making the eating experience odd.
Tony Roma's is not barbeque...they lasted like a total of 6 months in Kansas City.
Oh and Kansas City barbeque is the best!!!