You can see the Giant store coupon policy here, I recommend printing it out and carrying it with you when you shop.
Giant will double the face value of Manufacture’s coupons(however some will only allow 1 identical coupon to double per day, per customer), all FREE item coupons will be taken at face value. To use their double coupons you must have a store bonus card that is FREE to sign up for. Giant accepts printable coupons with a value less then $5. They do not accept internet printed coupons for free items.