Another way to double-dip on the iDine program is that some of the same restaurants also participate in Restaurant.com. (Usually local, non-chain restaurants that are trying to bring in customers.) Restaurant.com protip: only buy Restaurant.com certificates towards the end of the month when they are 80% off -- coming to ~$2 per coupon, IIRC. They do this annoying progression where they go full-price, 50% off, 70% off, 80% off, etc. each month. (Sign up for their emails so that you will be notified when the "sale" happens and so that you have the code for the sale -- easy to find anyway, but the e-mails save the time.) Note, though, that some of the more popular/expensive restaurants (e.g. French cuisine) limit Restaurant.com sales on a monthly basis, so you can only buy their certs at the beginning of the month at full price.... by the time the discounts hit, they are "sold out" for the month. Of course, using the certificate will lower your bill, and thus your miles earned -- but they can be pretty good deals.

Also note that there are always caveats to the Restaurant.com certificates which can make the deal less appealing. For example, many of them do not apply towards alcoholic beverages, and most apply an automatic gratuity before taking the discount. My favorite place (when I lived in the area) was a BBQ place with a $25 off $35 coupon. I could buy this coupon for $2 from Restaurant.com. My wife and I would eat together, and we would order an extra meal and an appetizer to get us over $35. With tax and gratuity we would usually end up paying in the $20 range, but we'd have an extra meal's worth of meat and sides to take home. We went there a lot. I didn't even realize that the restaurant also participated in AAdvantage dining until later when I saw the miles on my statement. Anyway, point is, read the fine print on Restaurant.com.