when i was in mexico city, i fell in love with good tequila. it's just tasty. but they serve it with some tomato-juice type thing that no one i've asked has heard of. i finally emailed my mexico city tour guide/friend and he filled me in...now you get a lesson in tequila, as well:
Its name is "Sangrita" and its a mixture between tomatoe juice, black pepper, salt and Tabasco sauce drops.
It's a shame that no one there has heard about it, cause its so famouse. But you can tell anyone that when you ask in a Mexican restaurant for Tequila shot, its mandatory that the waitress brings you two glasses (one with tequila and the other one with the "Sangrita").
Even when you ask in a restaurant for a tradittional "flag" (You know the three colors of the Mexican Flag: Green, White and Red) they will bring you three glasses: A lemon juice shot (Green), a Tequila shot (White) and a Sangrita shot (Red).