For home-cooked beans: Scoop out two cups with a little bean broth and reheat in a large pan for about 5 minutes, or until the liquid evaporates enough so the broth becomes a thick sauce. For canned beans: Drain and rinse the beans, then heat with 1/4 cup of chicken or vegetable stock. Season with salt and pepper, to taste.
Prepare the tortillas from scratch, or if using pre-made tortillas, warm them in a small pan over medium heat, about 30 seconds per side.
Assemble tacos by spooning 1-2 tablespoons of beans onto one tortilla, then topping with tomatoes, jalapeño, avocado, corn, and cilantro.
Squeeze some fresh lime juice onto your taco right before taking the first bite.