Though it's been mentioned in several recipes, I feel that aluminum foil is so useful for barbecuers that it deserves its own post.
I don't like using water pans. The water pan serves the purpose of steaming meat while it smokes. This may work best for large, slow-cooking meat cuts, though the steam could impede the formation of a good bark for quicker cooking meat like ribs. For whole turkeys, the long cooking time will take care of this problem. For those who do use water pans, more power to ya, keep on doing what you do. But for those of us who prefer to nix them, aluminum foil is your best friend.
Foil works to create a steamy environment once the meat has absorbed all the smoke it's going to absorb. This actually works particularly well for those of you who have a smoker which tends to run a little hotter than the usual "low 'n slow" temperature. Once a quality bark has been created, wrapping the meat in foil will lock in the remaining moisture, steaming your ribs or pork shoulder until they become tender. Additionally, I've found that it does not ruin that awesome, spicy bark.
For spare ribs, I allow the smoke to work its magic for about 3 hours before wrapping in foil. For pork shoulder, depending on the size, you can let it go for 4 or 5 hours before wrapping it for the duration of cooking time. For a big ol' packer brisket, 5 or 6 hours (which is about halfway done!).