Warm tortillas, without crowding, in a single layer on a medium-hot griddle or in a 10- to 12-inch frying pan over medium-high heat, turning once, until hot and flexible, 30 to 60 seconds per tortilla. As they're heated, stack in a basket lined with a thick towel (or in an insulated tortilla warmer); add more tortillas to griddle. Or divide tortillas into 3 equal stacks, seal each stack in foil, and heat in a 350° oven until hot in the center, 12 to 15 minutes; unwrap and stack in a towel-lined basket.
Place fillings, salsas, sauces, condiments, vegetables, and beans in separate containers and arrange on buffet (see notes); keep those that need to be warm on an electric warming tray or over a candle (stir occasionally to prevent scorching).
To assemble each taco, stack 2 tortillas on a plate and spoon filling down the center; add salsas, sauces, condiments, and vegetables to taste, and fold tortillas over filling to enclose. If desired, wrap with a napkin, and hold to eat.
Condiments and vegetables: 2 cups total (about 10 oz.) crumbled cotija cheese and/or shredded white or yellow cheddar cheese or jack cheese; 1 1/2 cups Mexican crema, jocoque, or sour cream; 6 cups total shredded iceberg lettuce, a mix of romaine lettuce and red cabbage, or green and red cabbage; 1 1/2 cups chopped onions (taquerias typically use those with white skins); 1 cup minced fresh cilantro; 2 cups diced firm-ripe tomatoes; 2 firm-ripe avocados (1 lb. total), peeled and coarsely mashed with 2 tablespoons lime juice; and 3 limes (3/4 lb. total), rinsed and each cut into 6 wedges.
Nutritional analysis per 2 corn tortillas.
Allow 3 tacos per serving. Arrange plates and warm tortillas at the head of the line, followed by fillings grouped with the salsas, sauces, condiments, and vegetables that suit each best (see suggestions in notes for each filling; however, all are interchangeable). End with the beans; set bowls and soup spoons alongside. And provide plenty of napkins to help keep drips under control.