Rule #1: NEVER make an online purchase without first searching the Internet for a promo code. You can make a general search under the store name + promo code, or online code, or coupon. Or you can visit Retailmenot.com for the most extensive list of online promo codes.
Rule #2: Always log into Ebates.com before making your purchase. You will save an additional 1-26% on your purchase in addition to the promo code savings.
Rule#3: Never assume that the site you are purchasing from will take only one promo code. Many sites allow promo code stacking. Some will only allow percentage off and free shipping stacking and some will allow percentage off stacking.