The first place one should look when trying to find dog food or cat food coupons would be the manufactures websites. Most manufactures have great deals and it will be made available first on the manufactures website. Most time they have the best dog food coupons.
We also want to note that we encourage everyone to check the FDA website regularly to make sure your dog food isn't on the recalls list. You can find the FDA page here: :www.fda.gov/Safety/Recalls/default.htm
Here is a good site they keeps consumer up to date on great coupon offers:
Secondly, would be social networks. Manufactures often sign up on twitter, facebook and tumblr. They will release coupons on these sites to try and get more followers or fans. It worth adding them as a friend or liking them to save a buck.
The third method is one people often forget. Simply ask the manufacture for dog food coupons or even cat food coupons. Most time they will be more than happy to send you whatever they have. If you are a happy customer that means more money for them.
The last place I wanted to mention is simply the grocery store. Many times manufactures will send them couponsin which they will display in the store. Its always worth it to keep an eye out for these coupons when you are at the grocery store.