This is what I understand to be a purist viewpoint. Of course all tacos are good, because...tacos.
  1. Smile, you're about to eat tacos.
  2. Start by ordering the lengua
    If they don't have lengua, give'em a disappointed but understanding look, and order carnitas. Enjoy those carnitas and never come back. If they do have lengua, it should be tender and flavorful. If this is true, you may have found a reputable purveyor of tacos.
  3. Handmade tortillas
    Not as important as the meats, but as with all grain-based food vessels, freshness is a key factor. Hand made tortillas are often a little thicker and don't require doubling up on tortillas. You will appreciate the softer texture and old world flavor. I can't even believe I'm saying this, but the tortilla should obviously be made from corn.
  4. No dairy
    Cotija and crema should be reserved for more elaborate dishes. Aht ah, no buts. A good taco will be garnished with raw minced onion and cilantro to compliment the skillfully prepared meat and tortilla. A lime wedge will be supplied to brighten the flavors, and radish may be included as a palette cleanser. These items also aid in digestion. The radish as roughage, and the lime, even though it is an acid, will convert to alkaline in the body and combat the acid left by the fatty meat.
  5. Salsa
    Sample all of the salsas, and figure out which is your favorite. Pick one that is within your spice tolerance. Don't mix and match, this isn't a kid's soda fountain. And don't waste salsa, take what you need and leave the rest.
  6. Mexi-Coke
    At this point you've probably been eyeing the glass bottle of Coca-Cola. Go for it, clearly you're not on the Clean Cleanse if you're eating tacos, and it's made with real cane, so no syrup guilt. Plus, it's the best food/beverage pairing that doesn't involve alcohol, and isn't milk and cookies.
  7. Other meats
    Try them all, but if ordering the tripe make sure they prepare it "crispy".