What is the best liquid to cook pulled pork in?

I'm planing on cooking a pork shoulder in my crock pot, but I'm having trouble picking a fluid to cook it in. Some people suggest no liquid, but I'm afraid it would be to dry. So far I've seen suggestions of water, root beer, beer, chicken broth, and barbecue sauce. Some recipes call for one kind of liquid first, and then adding the barbecue sauce afterwards and cooking it for a few more hours. Time isn't really a problem, and I'm old enough to buy the beer. What have you had the best success with?