Walmart accepts the following coupons:
* print-at-home coupons off of the internet
* manufacturer's coupons
*competitors coupons
*soft drink container caps
*checkout coupons or " catalinas"
*** Things to know about couponing at Walmart**
only 1 coupon per item 
NO limit to # of coupons in transactions
If  coupon value exceeds the price of the item, the excess may be given  to  the customer as cash or applied toward the basket purchase. ( Great way  to score some overage towards your other purchases)
For example: 
Buy pens that are 99 cents- you use a coupon that is 1.50 towards those pens= 51 cents towards your other items you are buying!