One of the biggest challenges in cooking old-school barbecue is maintaining a low, steady heat as your pork shoulder or beef brisket cooks. That's especially important with brisket, a tough and lean cut of beef that becomes even more leathery if it's exposed to high heat. One solution is to use an offset smoker, which removes the actual coals to a separate firebox and then routes smoke and heat through the main combustion chamber. With a bit of practice, you'll soon be able to maintain your brisket at the steady 225 degrees Fahrenheit it requires.
Trim the layer of fat covering the top of your brisket to approximately 1/4-inch thickness. Rub the exposed surfaces thoroughly with your favorite dry spice rub or seasoning paste, then cover the brisket and refrigerate it overnight so the flavors can meld and infuse into the beef.
Place the probe of a probe thermometer at each end of the smoker's cooking chamber, so you can monitor its temperature. Light your charcoal. Once it's covered with a good layer of ash, adjust your smoker's vents until the cooking chamber stabilizes at 225 degrees Fahrenheit.
Open the lid and put your brisket in the cooking chamber, then quickly close the lid again. The temperature inside the cooking chamber cools briefly because of the escaping heat, but don't adjust the vents. The heat will return slowly to the previous level.
Slow-cook the brisket until it's fork-tender, usually at an internal temperature of 195 F to 205 F. This can take as long as 18 to 20 hours for a whole brisket, or 10 to 12 hours for smaller portions. Light fresh batches of charcoal periodically in a chimney style starter, then use those to replenish the coals in your cooker's firebox.
Remove the brisket from your smoker and wrap it tightly in aluminum foil, then in several clean towels. Place the bundle in a warmed picnic cooler, and let the meat rest for 1 to 2 hours before slicing it. This is optional, but the rest period makes your brisket noticeably more tender and juicy.