Taco Bell's are for teenagers and adults in their 20's who want to eat cheaply. Pass on the sour cream. Ranch and blue cheese are great but not on Tacos. Guac and salsa are the way to go.
Rarely eat tacos with Ground beef. Fish tacos are great as are tacos with Brisket, steak, pork carnitas or chicken. Of course most those are on soft corn or flour tortillas. For hard taco shells, shredded beef or Chicken Tinga (shredded chicken) are great. Pork carnitas work also. I might buy a Picadillo taco which uses ground beef. Chicken tinga and pork carnitas can be made in the slow cooker so not much prep time.
Breakfast tacos are great. There are Taco trucks and Taquieria's on every corner. Nothing like a Chorizo, black bean and scrambled egg taco with salsa. Well fajita, fried egg and black bean is really good combo. too.
When i moved to Austin in 2007 there was this Taco Truck. Torchy's Tacos. It is expanding everywhere now. Seems they made to Indiana. They have the best Green Chile cheese for dipping chips. A trashy trailer park with fried chicken is quite good.