Where: El Rio Grande (160 East 38th St.)
When: Anytime
How to Pull It Off: This one requires a little photo research on your end. Check-in with foursquare, and hunt down a picture of the El Rio Grande River. Show it to your server and get a free dessert. Chips and salsa are also complimentary, so you'll have a Mexican three course meal for nearly nothing. If tequila counts as your entree, that is.