In my experience they are just a random selection of restaurants that have done deals with AM for whatever reason (sometimes they are new restaurants or for some other reason trying to get new customers). If I really can't make up my mind between two places then I have occasionally used the AMs as the deciding factor, but it really isn't worth much if you do the sums. If you price AMs at 1 US cent each then you get just under 5% back on the price, but there's a minimum spend, and you could easily adjust the bill that much by, say, your choice of wine. Moreover, AM restaurants tend to be relatively expensive (although also relatively good).