Hi Janet;
I don't do this with expensive cuts of pork, I like to use what is called a boston butt because it is a moister softer roast and more suitbale for barbecue however a shoulder roast would work okay too.
I rub it with salt, pepper and garlic powder, put in the crockpot with maybe a cup of water and add a chopped up large onion. Cook on low 8-10 hours depending on the size, discard liquid, remove fat, shredd it up with two forks, put it back in the pot and add your favorite homeade or bottled barbecue sauce(I use whatever brand was on sale or I had a coupon for)Heat for a couple of hours on low.
Sometimes I make it ahead, transfer to a casserole and refrigerate for a day or two so the sauce can soak in and then reheat either in the crockpot or in the microwave. If you do it ahead you may have to add a little more sauce before you reheat it.