Make the tostada shells: Preheat the oven to 400 degrees. Lightly spray the corn tortillas on both sides with cooking spray or brush with olive oil. Place a single layer on a baking sheet. Sprinkle lightly with salt and pepper. Bake for 6 minutes. Flip over and bake another 4-8 minutes until crispy. For more traditional fried tostadas, heat about 1 inch of vegetable oil in a skillet. Once hot, add the corn tortilla and cook for 30-60 seconds until it begins to bubble and lightly brown. Flip with tongs and repeat on the other side. Set to dry on a paper towel.
Bean layer: Add a layer of refried beans, black beans, pinto beans, or any other beans you like. For whole beans, it is best to mash them lightly with a fork so that they don't slide off the tostada shell. If you don't love beans, add a layer of guacamole, melted cheese, or salsa to help your toppings stick to the shell.
Toppings: Finish the tostadas with any toppings you like. The most popular toppings include shredded lettuce, diced tomatoes, salsa, cilantro, sour cream, jalapenos, shredded cheese, queso fresco, avocado, guacamole, and pickled red onions.