If you are cooking at 225-250, it is going to take about 1 1/2 -2 hours per lb. of meat.

You want to cook this type of pork until it is 200 degrees internal temperature. This might sound counter-intuitive if you like a medium-rare steak. This is not a pork or beef tenderloin. You will get more tender and juicy meat by cooking it until it is 200 degrees. This type of muscle needs low heat and a lot of time to break down the tough muscle fibers. This is what all of the bbq experts will tell you.

Don't necessarily stick to a certain time for cooking for each cut of pork shoulder you cook. I've seen them weigh anywhere from 5-10 lbs.

Look online for homemade dry rub recipes containing ingredients like brown sugar, chili powder, paprika, etc...That will get you a good bark if you don't wrap it for too long.