Heat a dry, cast iron or other heavy skillet over medium-high heat. Add one corn tortilla and cook for about 30 seconds to soften and lightly char, flip tortilla and cook for about 30 seconds more. Transfer to aluminum foil to keep warm; repeat with remaining tortillas. (recipe note #1)
Meanwhile, heat oil in a large cast iron or non-stick skillet over medium heat. Add carnitas; cook and stir until the meat is heated through and has crispy edges. Add carnitas cooking liquid or broth as desired if the meat seems dry. (recipe note #2)
To assemble tacos, add 1/3 cup carnitas to a warm tortilla and layer on desired toppings. Repeat with remaining tortillas and serve. (recipe note #3)
If you're feeding several people, you can warm the corn tortillas in the oven. They won't have that pleasant char, but they'll be soft, warm, and delicious anyway. To do so, wrap stacks of 6 tortillas in foil and heat in a 350˚F oven for 8 to 10 minutes.
I prefer to pan-crisp carnitas, but you can also warm and crisp it under the broiler. Spread the carnitas in a shallow layer on a foil lined baking sheet and broil on high for 3 to 5 minutes until warmed through with crispy edges. Add carnitas cooking liquid or broth as desired.
Or serve family style with warmed tortillas in foil and warm meat and toppings in separate serving bowls for everyone to assemble their own tacos.
Note that nutrition facts do not include toppings.