It is a very good idea to have the store’s coupon policy in hand anytime you are extreme couponing. There is always a chance anytime you go into a store to use coupons, that the cashier is not actually going to know what the store policy is. If you have it from their website or a copy of an email they sent you, you will be able to get a lot farther than by saying “but I always do it this way here.”
If you need to contact the store to ask them, do it by email so it is in writing. Ask questions about manufacturer coupons, printable coupons and any loyalty card perks. Ask specific questions about printable coupons like if they allow free product coupons and if you can print them in black and white.
Find out if they give credit if the price of the coupon is more than the item. See if they match any other ads or accept coupons specific to other stores. Ask if there is a limit on coupons per transaction. Basically, think of how you are going to use coupons and imagine any issues that could arise, and ask about them in advance and get it in writing.