I've added a few coupon policies to the sidebar over there for your enjoyment. I have always said you should print these out and have them with you in the store at all times. Unfortunately, I don't take my advice. All it takes is one time of frustration when you (I) know you are (I am) right and you'll (I'll) be kicking yourself (myself) in the rear end.
Notice that there are a couple of stores missing on that list...
Walgreens and Food Lion, for example, do not have official corporate coupon policies. Which is just great, because you can go to two Food Lions 20 yards from each other and it will simply depend on the manager of that store as to what coupons you can use. I did find two Food Lion coupon policies on blogs but they were conflicting, so I don't want to post either one as I'm not sure what information is accurate.
These are the stores that are semi-local, which is why I chose to put their policies up. If you think another should be added just let me know!