One of my favorite ways to make a BBQ sauce is to apply a dry rub to the meat (pork, beef, whatever) 2 days before hand. Then once you've got the meat in the smoker, take all the liquid that is in the bag/tupperware you had your dry rub in and put it in a sauce pot. Add ketchup, mustard, molasses and sugar (or brown sugar with some extra molasses), apple cider vinegar, some of your favorite beer, then spices to taste (cumin, ground mustard, chili powder, paprika, chipotle pepper, cinnamon, garlic powder or salt, onion powder or salt, allspice, etc...). Make sure this comes to a boil because it has a lot of the animal juices in it. Once at a boil, you can either reduce it to a thick sauce, or leave it thin (think pulled pork).

The best way to learn is just trial and error and throwing crap in and tasting constantly. Alton Brown for his dry rub suggests that as long as you keep this ratio: 8 parts (sweet) + 3 parts (salt) + 1 part (spicy) + 1 part (other spices/flavors), you'll be okay.

You could take alton's ratio and then apply it straight to sauce, without doing the dry rub step. Then, if you like it spicy, make sure you alter the recipe slightly to do that. Also, in the sweet category you can do more than just brown sugar, you could use honey for part of it, or some kind of fruit. For the salt you could use garlic salt for part of it, or onion salt. For spicy, feel free to use your favorite chili mix. So long as 8,3,1,1 is kept though, you usually won't miss.

Good advice from D-Dub too. As he said, BBQ is personal, so take what you get from other recipes, then ad-lib.