Here is a copy of the Walmart coupon policy. Also make sure to go to their website and print one off to keep with you and be sure to update it periodically.

Wal-Mart Coupon Policy Wal-Mart accepts the following types of coupons (see guidelines below): Manufacturer coupons (Cents Off) Free merchandise (or manufacturer's Buy-One-Get-One-Free) coupons Store coupons Pharmacy (Advertising and Promotional) coupons Internet coupons Soft drink container caps The following are guidelines and limits: Wal-Mart only accepts coupons for merchandise we sell and only when presented at the time of purchase. Coupons should have an expiration date and be presented within the valid dates. Wal-Mart will not accept expired coupons. Internet coupons should be legible and say "Manufacturer Coupon." There should be a valid remit address for the manufacturer and a scannable bar code. Only one coupon per item is permitted. Use of 40 or more coupons per transaction will require approval by Customer Service Manager.