Add taco seasoning according to packet directions.
While beef is simmering put refried beans in a small sauce pan to warm over low heat. May need to add 1-2 tablespoons of water to the beans to thin them out a bit.
Warm soft tortillas in a dry skillet over low to medium heat. You don't want to brown or crisp them at all. Just warm them on both sides so that they are pliable.
Keep tortillas warm in foil. These can be placed in a warm oven if needed.
Assemble the tacos:
Spread warm beans on a warm flour tortilla (Like spreading pizza sauce on pizza dough).
Sprinkle beans with shredded cheese.
Stand a taco shell in the center of tortilla spread with beans and cheese.
Gently press the soft tortilla onto the sides of the taco shell.
Fill taco shell with beef, more shredded cheese, shredded lettuce and salsa.
*variation* if you prefer not to use refried beans just use all cheese to "glue the soft tortilla to the taco shell. If you choose this option just cover the tortilla with a layer of shredded cheese while warming in skillet. As soon as the cheese is melted remove from skillet and place your taco shell in the middle, quickly folding up the sides so they stick to the taco shell. Fill taco and enjoy!