Smoke is a necessity of barbecue. What type of wood you use for smoke is up to you. What works best, however, are the Southern traditional woods: hickory and oak, particularly white oak. Also, pecan, walnut, cherry, apple, and peach are good choices. You should stay away from alder and mesquite because they tend to add a strong flavor to meats. Despite how long the meat is cooked, it should be exposed to smoke for at least the first six hours.
Purists will say that your fire should be made entirely from hardwood logs that have been burned down to coals and then added to the smoker. Of course, this isn't practical for everyone. Whether limited by equipment or temperament, many people find it difficult to burn hardwood logs for the kinds of coals used by diehard traditionalists. If you do go with charcoal, you will benefit most from hardwood charcoal, but you can, if need be, use regular charcoal. It's ideal to stay away from charcoal with additives like lighter fluids. If you are using charcoal, add presoaked hardwood chunks (not chips) to the coals once the fire is good and hot. Make sure to drain off as much water as possible. The wood should be moist, not wet. During a long smoking period, you will probably have to add additional burning coals to the fire to maintain the temperature and additional wood chunks to maintain smoke.
Once the smoker is ready, add the meat. The ideal smoking temperature is around 215 degrees F with the acceptable ranges being between 215 degrees F and 235 degrees F. Under normal conditions, you should plan on smoking for about 1 to 1-1/2 hours per pound. Of course, the temperature modifies the cooking time.
If you smoke on the higher end of the temperature range subtract about 10 minutes per pound. This means a 10-pound pork shoulder can take 15 hours to finish. Many people find it difficult to maintain a good temperature for this long and choose to wrap the pork in foil and place it in the oven. As previously stated, you should keep the meat in the smoker for at least 6 hours. Though there is still debate on the subject, conventional wisdom suggests that the amount of smoke flavor absorbed by meat declines as it cooks. Therefore, the amount of smoke flavor added in the last two hours is relatively insignificant. However, in most cases, it is best to keep meat in the smoker for as long as possible. If it becomes difficult to maintain the temperature or other circumstances get in the way, move it to the oven. If you do transfer the meat to the oven, set the temperature in the ideal temperature range. Make sure you wrap the pork tightly in foil to hold in the moisture. Many people, even competition cooks, will smoke their pork roasts unwrapped for half the overall cooking time and then wrap.
Once the meat reaches an internal temperature around 180 degrees F to 190 degrees F, it is ready to be pulled.
You can serve the meat once it reaches 165 degrees F, but it won't be tender enough to pull apart properly. Typically, you can pull the meat easily once the internal temperature reaches 190 degrees F, but you don't want to go above this as the higher the temperature becomes the greater chances of the meat drying out. So, always keep an eye on it.
Once the pork is cooked, remove it from the smoker (or oven as the case may be) and let it sit for about an hour. This will cool it down enough for pulling. As you pull the meat apart, place it in a pot on a low temperature to keep it warm. You will need to separate the meat from remaining fat, bone or other unpalatable parts. From here you can serve, however, many people prefer a finishing sauce, so it's best to have one ready.