We love tostadas as a light summer meal, especially when it gets near 100°F. In the winter we usually we bake them in the oven; you can also deep fry them but they often get bubbles that way which makes them structurally weak.
My current favorite is to pan fry them, it doesn't heat up the kitchen so much and is pretty fast. A little oil brushed on and cooked in the pan. I noticed that it was beginning to curl so I put the bacon press on top, they turned out nice and flat and crispy.
There are a architectural rules you need to follow when building a successful tostada. Refried beans are great for forming a foundation, they are sticky so the food stays on the tortilla and not just slid off. It will also hold the tortilla together a little when it breaks. But after a layer of meat, cheese and salsa the beans will be blocked so they can't hold onto the higher toppings.
Now a layer sour cream or guacamole under the top layer of lettuce and tomatoes and the whole thing holds together even if you drop it, which of course I did. I just used my fork to flip it back over and expect for a few stray bits of lettuce it had held together.
