Taco salad:

First throw the "store-bought" shells (and they do often taste as exciting as chewing clam shells) in the trash. Simply serve a good grade of warm, thin "chips" from tortillas de mais (corn!).

Layer in large shallow bowl:

Chopped or shredded romaine
Optional : Black beans or well seasoned pintos or Salvadorean "Little Reds", but not "Refritos"
Shredded chicken, sliced carne asada (Broiled beef), or carnitas (pork), all of which have been well seasoned during/before cooking.
Sliced ripe avocado
Pico de Gallo (Chopped onion, chopped jalapeno, chopped tomatoes, chopped cilantro, salt, fresh lime juice and a bit of olive oil when destined for a "taco salad")

Topped with crumbled "Queso Cotija", a Mexican cheese resembling (when young) a less salty Feta.

Sour cream seems a traditional US topping, but it doesn't work for me, just as most of the ground beef-based "taco meats" don't live up to my expectations. Sauteed sweet peppers or poblanos and onions simply don't go well with a salad, just as the barbaric custom of adding sweet corn or corn based relishes is anathema. Shredded US Cheddar or Monterrey Jack simply don't have enough flavor, and if I can't find "Cotija", I would substitute feta.